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core-js

Core-js is a widely utilized JavaScript library that serves as a modular standard library, providing polyfills for many features of ECMAScript that are missing in older browsers. This library is especially valuable for developers who need to ensure their web applications function seamlessly across different browsing environments. Core-js offers a robust set of features including polyfills for promises, symbols, collections, iterators, typed arrays, and various other ECMAScript proposals that have not been universally adopted by all browsers.

Core-js was created by Denis Pushkarev, also known as zloirock, and was first introduced in the year 2014. The project was developed to aid in the compatibility of JavaScript codes across different browser versions by implementing polyfills that emulate missing functionalities in older browsers. As a result, developers can write modern JavaScript code without having to worry about the support of these features in legacy environments. This library has become a fundamental tool for web development, facilitating the use of the latest JavaScript standards even in browsers that are not up to date with the latest ECMAScript specifications.

Core-js is a vital JavaScript library designed to ensure web applications are compatible across various browsers by providing polyfills for ECMAScript features that may be lacking in older environments. It acts as a bridge allowing developers to utilize modern JavaScript features without worrying about browser compatibility issues. This library covers a wide range of JavaScript functionalities, from basic language features to complex constructs like promises and iterators.

The library was developed by Denis Pushkarev, also known as zloirock, who launched Core-js in 2014. His vision was to create a comprehensive tool that would allow developers to leverage the latest ECMAScript standards effortlessly across all browsers, regardless of their native support for these standards. Denis Pushkarev continues to actively maintain and update the library, ensuring it remains relevant as new ECMAScript proposals become standardized.

Core-js provides a plethora of features essential for modern web development. These include polyfills for ECMAScript 2015 (also known as ES6), ECMAScript 2016 (also known as ES7), and features from later versions up to the latest drafts of ECMAScript. By including Core-js, developers can use features like symbols, sets, maps, and typed arrays in environments that do not yet support them natively.

Integrating Core-js into a project is straightforward. Developers typically include it at the base of their JavaScript code to ensure all subsequent code can utilize the polyfills. It is compatible with Node.js and can be included in web projects using bundlers like Webpack or Rollup. The modular nature of Core-js allows for selective inclusion of polyfills, which helps in keeping the bundle sizes minimal by only including the features needed for a particular project.

A key aspect of Core-js is its ability to polyfill newer ECMAScript features back to ECMAScript 5, enabling functionalities that are otherwise unsupported in older browsers like Internet Explorer. This backward compatibility is crucial for maintaining accessibility and functionality across diverse user bases, especially in corporate environments where older browsers are still in use.

Core-js has significantly impacted web development by reducing the time and effort developers spend on ensuring cross-browser compatibility. It supports the progressive enhancement strategy in web design, where applications are built for the lowest level of user capability but can enhance their operation with more advanced browser features when available.

Core-js is regularly updated to include polyfills for the latest ECMAScript features as they move through the proposal stages and become part of the language standard. This ongoing maintenance helps developers stay ahead of the curve by allowing them to adopt new features shortly after they are proposed. Denis Pushkarev’s commitment to the project ensures it is one of the most up-to-date polyfill libraries available.

The development of Core-js is supported by a community of developers who contribute to its growth through code contributions, bug reports, and feature requests. This community involvement helps in refining the library and extending its capabilities to cover more features and ensure greater compatibility.

While Core-js provides extensive support for many features, it is not without its limitations. The library can increase the size of web application bundles significantly, particularly if many polyfills are used indiscriminately. Developers need to balance the need for compatibility with the performance implications of adding extra JavaScript code to their projects.

As ECMAScript continues to evolve, Core-js will also need to adapt by incorporating new standards and features. The future of Core-js is likely to involve more intelligent polyfill mechanisms that can more accurately detect and load only the necessary features based on the user’s browser capabilities, potentially integrating with dynamic import systems.

Many popular frameworks and libraries, including Babel, use Core-js as a base for their polyfill strategies. For instance, when a developer uses Babel to transpile modern JavaScript code to be compatible with older browsers, Babel includes relevant polyfills from Core-js based on the targeted browser environments specified in the project's configuration.

Core-js is well-documented, with extensive resources available online to help developers understand and implement the library effectively. The documentation covers installation, usage examples, and a comprehensive list of features that the library supports. This makes it accessible to both novice

and experienced developers.

Core-js stands out as an essential tool in the modern web developer’s toolkit, bridging the gap between the latest JavaScript developments and the diverse landscape of user browsers. Its ability to enable future-proofing of web applications while maintaining broad compatibility has made it a staple in the industry.

core-js Alternatives - Alternatives to core-js

While Core-js is a popular choice for providing polyfills in web development, there are several alternatives that developers might consider based on their specific needs or constraints. These alternatives also offer polyfills for various ECMAScript features, but they may differ in terms of scope, performance, and the specific methods they use to implement the functionalities.

One prominent alternative is Babel-polyfill, which integrates seamlessly with Babel, a JavaScript compiler commonly used to convert modern JavaScript into backward-compatible versions for older browsers. Unlike Core-js, which can be used independently, Babel-polyfill is typically used in conjunction with Babel's transpilation processes. This integration allows it to provide more targeted polyfills based on the specific features that are being transpiled by Babel.

Polyfill.io is a service that takes a different approach by dynamically serving only the necessary polyfills based on the browser making the request. This feature is particularly useful for reducing the size of the JavaScript bundle, as it ensures that browsers only load the polyfills they need. This can significantly improve page load times and overall performance, especially in modern browsers that may require fewer polyfills.

The ES-Shims project provides a collection of shims and polyfills for a broad range of ECMAScript features. It is particularly comprehensive, covering more speculative or less commonly used features that might not be included in other libraries. ES-Shims can be a good choice for developers who need to ensure compatibility for specific or advanced ECMAScript features not fully supported by other polyfill libraries.

Modernizr is another tool that developers use for browser feature detection rather than directly providing polyfills. It allows developers to add classes to the HTML document based on whether certain features are supported in the browser or not. From there, developers can decide to load specific polyfills or alternative styles/scripts as needed. This method is highly customizable and enables developers to build a more tailored experience based on the user's browser capabilities.

core-js Command-Line Interface - core-js CLI:

Create a list of the top 40 core-js CLI commands with no description or definitions. Sort by most common. Include NO description or definitions. Put double square brackets around each topic. Don't number them, separate each topic with only a comma and 1 space.

core-js Command-Line Interface - core-js CLI:

Summarize this topic in 15 paragraphs with descriptions and examples for the most commonly used CLI commands. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Best Practices:

Core-js is a JavaScript library that provides polyfills for the latest ECMAScript features, allowing developers to use these features in environments where they are not natively supported. It is essential for maintaining compatibility across various browsers, especially older ones, ensuring that users have a consistent experience regardless of their browser's capabilities.

When using Core-js, it is crucial to import only the specific polyfills you need. This approach, known as modular imports, helps reduce the overall size of your JavaScript bundles. Core-js is designed to be modular, allowing you to include individual features rather than the entire library, which optimizes both loading times and performance.

Integrating Core-js with build tools like Webpack or Rollup is a standard practice. These tools can automatically include the necessary polyfills as part of the build process. Configuration options within these tools allow developers to specify which environments they are targeting, thus tailoring the polyfills to only those needed for compatibility.

Babel is often used alongside Core-js for transpiling modern JavaScript code into a form that can be understood by older browsers. When setting up Babel, you can specify which version of Core-js to use, ensuring that the polyfills are aligned with the ECMAScript features you are using in your project.

Keeping the Core-js configuration up to date is crucial. This includes regularly updating the version of Core-js as part of your project dependencies to benefit from the latest polyfills and bug fixes. Failure to update can lead to compatibility issues or missing features, which could degrade the user experience.

Thorough browser testing is essential when using Core-js. Developers should test their applications across all supported browsers to ensure that polyfills are functioning correctly. This process helps identify any gaps in the polyfill coverage or issues with specific browser versions.

Understanding the scope and limitations of each polyfill in Core-js is important for effective use. Some polyfills may have limitations in how accurately they mimic native implementations, which could affect application behavior. Developers need to be aware of these limitations to avoid unexpected bugs.

For projects that need to support legacy browsers, such as older versions of Internet Explorer, Core-js is particularly valuable. However, it's important to balance the need for these polyfills with the performance implications of loading unnecessary code in modern browsers that do not need them.

Performance optimization is critical when using polyfills. Developers should measure the impact of adding Core-js on page load times and overall application performance. Techniques such as lazy loading of polyfills based on feature detection can help mitigate performance penalties.

Utilizing the documentation provided by Core-js and participating in community discussions can greatly enhance a developer's ability to use the library effectively. The Core-js GitHub page and other online forums provide valuable resources for troubleshooting and learning best practices.

Developers must consider the security implications of using polyfills. Since Core-js modifies native JavaScript environments, it's important to ensure that these changes do not introduce security vulnerabilities, particularly when dealing with sensitive data.

Contributing to the development of Core-js can benefit the wider community. By submitting bug reports, feature requests, or patches, developers can help improve the library and ensure it continues to meet the needs of a diverse developer community.

Organizations should consider training their development teams on best practices for using Core-js. Sharing knowledge about how to effectively integrate and leverage polyfills can lead to more robust and compatible web applications.

Staying informed about future trends in ECMAScript and Core-js is crucial. As the JavaScript landscape evolves, Core-js will continue to adapt, adding new features and improving existing ones to better serve the development community.

In conclusion, using Core-js effectively requires understanding its capabilities and limitations, integrating it properly with other tools, maintaining an up-to-date configuration, optimizing for performance, and engaging with the community. By following these best practices, developers can leverage Core-js to build robust, compatible, and efficient web applications.

core-js Anti-Patterns:

Using Core-js effectively requires understanding not just what to do but also what to avoid. Common anti-patterns can undermine the benefits of this powerful polyfill library. Recognizing these pitfalls is crucial for maintaining optimal performance and compatibility in web development projects.

One of the most frequent anti-patterns is over-polyfilling, where developers include more polyfills than necessary. This can lead to bloated JavaScript bundles, negatively impacting the load times and performance of web applications. Developers should carefully select only the polyfills that are necessary for the browsers they are targeting, rather than including the entire Core-js library by default.

Improper configuration of Core-js with Babel can lead to significant issues. A common mistake is not specifying the correct version of Core-js or misaligning it with the project's ECMAScript feature usage, resulting in either missing polyfills or redundant code. Ensuring that Babel's configuration is carefully aligned with the Core-js version can prevent these issues.

Another anti-pattern is ignoring browser-specific needs by using a one-size-fits-all approach to polyfills. Different browsers have different levels of support for ECMAScript features, and using the same set of polyfills for all can lead to unnecessary code execution and wasted resources. It's more efficient to tailor polyfill inclusion based on the specific requirements of each browser version.

Failing to thoroughly test web applications across all targeted browsers is a critical oversight. This can lead to situations where certain features do not function as expected due to inadequate or incorrect polyfill coverage. Regular and comprehensive testing ensures that polyfills are effectively supporting the application as intended.

Not performing performance benchmarking after integrating Core-js is a significant anti-pattern. Without benchmarking, it's challenging to understand the impact of polyfills on the application's performance. Developers should regularly measure performance to ensure that the inclusion of Core-js does not adversely affect user experience.

Lastly, a common mistake is to continue polyfilling features that modern browsers already support natively. This not only wastes resources but also potentially conflicts with native implementations, which are typically more efficient. Developers should periodically review and update their polyfill strategy to exclude features that have become widely supported in updated browser versions.

core-js Security

Security is a paramount concern when using any third-party JavaScript library, including Core-js. Since Core-js modifies the native environment of ECMAScript to implement its polyfills, it's essential to understand the security implications of these modifications. Ensuring that Core-js does not introduce vulnerabilities is crucial for maintaining the overall security of web applications.

Polyfills can potentially introduce vulnerabilities if they are not implemented correctly. Since Core-js aims to mimic native ECMAScript behaviors, any discrepancies or flaws in the implementation could be exploited by attackers. It is vital to ensure that the polyfills used do not open up security holes, particularly in areas like object prototypes or global environment modifications.

One of the key security practices with Core-js is to keep the library updated. Each new release can contain patches for security vulnerabilities that were discovered in earlier versions. Regular updates ensure that security patches and improvements are applied, reducing the risk of exposing web applications to exploits through outdated code.

When integrating Core-js with Babel, it's important to configure both tools securely. Misconfigurations can lead to unintended global exposures or conflicts that might be exploited. Ensuring that the setup only includes necessary polyfills and follows security best practices can help mitigate such risks.

Since Core-js is a third-party library, it's important to review its code and understand its functionality before integrating it into your projects. Awareness of what the library does, especially how it interacts with the global scope and native objects, is crucial for maintaining security. Trusting the library without understanding its implications can lead to security lapses.

Implementing thorough testing procedures to check for security flaws in the areas affected by Core-js polyfills is essential. Security testing should be a part of the development cycle, ensuring that the introduction of polyfills does not inadvertently compromise application security. This includes both static analysis and dynamic testing methods.

Core-js sometimes provides polyfills for deprecated or soon-to-be-deprecated ECMAScript features. Using deprecated features can be risky as they may not receive security updates or support. Developers should be cautious about using polyfills for deprecated features and consider the security implications of maintaining such code.

Finally, educating developers on secure coding practices related to the use of Core-js and polyfills is crucial. Understanding the best practices for secure use of third-party libraries, regular updates, and secure coding can help mitigate potential security risks associated with using Core-js in web development projects.

core-js Programming Languages:

Discuss which programming languages are supported. Discuss which programming languages are most commonly used. Summarize this topic in 4 paragraphs. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js and Unit Testing:

Core-js is a library that provides polyfills for JavaScript, ensuring that features from the latest ECMAScript standards can be used in environments that do not natively support them. While Core-js itself is not a unit testing framework, it plays a crucial role in testing environments by allowing developers to test JavaScript code that uses newer language features across multiple browser versions. This capability is especially important in unit testing scenarios where consistent behavior across environments is necessary for accurate testing outcomes.

When setting up a unit testing environment for a project that uses Core-js, developers typically integrate it with a testing framework like Jest, Mocha, or Jasmine. These frameworks handle the execution of tests and provide useful features such as mocks, spies, and assertion libraries. Core-js is included in the project's setup files to ensure that all tests run with the necessary ECMAScript polyfills in place, allowing tests to run smoothly even in older execution environments:

```javascript // Example of integrating Core-js with Jest in jest.config.js module.exports = {

   setupFiles: ['core-js']

// Using an ES2020 feature in a test test('array.includes works correctly with NaN', () ⇒ {

   expect([NaN].includes(NaN)).toBe(true);

This configuration ensures that features like `Array.prototype.includes` are available during tests, replicating a fully ES2020-compliant environment.

Testing in environments enhanced by Core-js can introduce specific challenges. One such issue is ensuring that the polyfills do not alter the behavior of the application in ways that would not be representative of an environment where native support for the features exists. It is also crucial to make sure that Core-js does not interfere with the mocking or stubbing of built-in JavaScript objects, which can lead to brittle tests that fail in real-world scenarios:

```javascript // Potential pitfall when testing with polyfills test('String.prototype.replaceAll is not incorrectly mocked', () ⇒ {

   const originalReplaceAll = String.prototype.replaceAll;
   String.prototype.replaceAll = () => 'mocked';
   expect('real'.replaceAll('re', 'fa')).toBe('mocked'); // This test may fail unexpectedly in native environments
   String.prototype.replaceAll = originalReplaceAll;

Developers need to carefully design their tests to account for the presence of polyfills, ensuring that they do not inadvertently test the polyfill rather than the actual application logic.

To effectively use Core-js in unit testing scenarios, it is essential to maintain clear separation between tests that check polyfilled functionality and those that test application-specific logic. Utilizing conditional test patterns based on feature detection can also help differentiate between environments that require polyfills and those that do not:

```javascript // Conditional testing based on feature availability if (!String.prototype.replaceAll) {

   test('replaceAll polyfill behaves as expected', () => {
       expect('test'.replaceAll('t', 'b')).toBe('besb');
   });

By carefully managing the use of Core-js in unit tests and ensuring that tests are aware of the environment, developers can maximize the reliability and relevance of their test suites across various JavaScript execution contexts.

core-js and Performance:

Core-js is widely used to provide polyfills for newer ECMAScript features in environments that do not support them natively. While it is an invaluable tool for achieving cross-browser compatibility, it is important to consider its impact on performance. Integrating Core-js can potentially increase the execution time and resource consumption of web applications, especially if a large number of polyfills are loaded, regardless of whether they are used by the client's browser or not. Developers need to balance the benefits of using Core-js with the possible drawbacks related to increased page load times and execution overhead.

One effective way to mitigate performance issues when using Core-js is to selectively load polyfills based on the features that are actually needed by the application and supported by the user’s browser. This approach minimizes the unnecessary code sent to the client, reducing load times and parsing overhead. For example, before loading a polyfill, a check can be performed to see if the browser already supports the feature:

```javascript if (!Array.prototype.flat) {

   require('core-js/features/array/flat');

This code checks if the `Array.prototype.flat` method is missing, and only loads the polyfill if it is not natively supported, thereby ensuring that only necessary polyfills are loaded.

The indiscriminate inclusion of Core-js can significantly increase the size of JavaScript bundles, affecting the application’s load time. Moreover, since polyfills simulate native features using JavaScript, they can be slower than their native counterparts. It's important to analyze the performance implications of each polyfill:

```javascript // Measuring performance of a polyfilled feature console.time('flat'); [1, [2, [3, [4]], 5]].flat(Infinity); console.timeEnd('flat'); // Outputs the time it takes to flatten an array ```

This example measures the time it takes to flatten a nested array using the `flat()` method provided by Core-js. Monitoring such metrics helps in understanding the cost of using polyfills in terms of execution speed.

To optimize the use of Core-js and mitigate its impact on performance, it is advisable to integrate only the necessary modules. Utilizing tools like Webpack or Rollup allows developers to include polyfills only for the specific features used by the application, which are not natively supported by the target browsers. Additionally, developers should regularly review the polyfills included in their projects as browser technologies evolve, potentially making some polyfills obsolete:

```javascript // Using Webpack to only include necessary polyfills module.exports = {

   entry: 'index.js',
   module: {
       rules: [
           {
               test: /\.js$/,
               use: {
                   loader: 'babel-loader',
                   options: {
                       presets: [
                           ['@babel/preset-env', {
                               useBuiltIns: 'usage',
                               corejs: 3,
                               targets: "> 0.25%, not dead"
                           }]
                       ]
                   }
               }
           }
       ]
   }

This configuration uses Babel along with Webpack to automatically determine and include polyfills needed for the browsers specified in the `targets` option. This method ensures that only the necessary parts of Core-js are bundled, enhancing performance.

core-js and WebAssembly:

Discuss how WebAssembly / Wasm is supported by core-js. Give code examples. Summarize this topic in 4 paragraphs. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Automation with Python

Summarize this topic in 3 paragraphs. Give 3 code examples. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Automation with Java

Summarize this topic in 3 paragraphs. Give 3 code examples. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Automation with JavaScript

Summarize this topic in 3 paragraphs. Give 3 code examples. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Automation with Golang

Summarize this topic in 3 paragraphs. Give 3 code examples. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Automation with Rust

Summarize this topic in 3 paragraphs. Give 3 code examples. Make the Wikipedia or other references URLs as raw URLs. Put a section heading for each paragraph. Section headings must start and end with 2 equals signs. Do not put double square brackets around words in section headings. You MUST put double square brackets around ALL computer buzzwords, product names, or jargon or technical words.

core-js Glossary:

ECMAScript: A standardized scripting language used to implement the core functionality of JavaScript, providing the specifications that JavaScript engines should follow.

Polyfill: Code that implements features in older browsers that do not support those features natively, allowing developers to use modern ECMAScript features in environments that are otherwise unsupported.

Babel: A JavaScript compiler tool that transforms modern JavaScript code into backward-compatible versions for older browsers, often used in conjunction with polyfills like Core-js.

Shim: A library that brings a new API to an older environment, using only the means of that environment.

Transpiler: A type of compiler that takes the source code written in one language and transforms it into equivalent code in another language, typically used for converting newer ECMAScript syntax into older syntax that can be executed by legacy browsers.

Module: In JavaScript, a file or script that encapsulates code and functionality, which can be imported and used in other JavaScript files, allowing for better code organization and reusability.

Webpack: A static module bundler for modern JavaScript applications, which compiles modules with dependencies to generate static assets representing those modules.

Polyfill.io: A service that automatically provides only the necessary polyfills based on the browser's user-agent string, optimizing load times by loading only required code.

Node.js: An open-source, cross-platform, back-end JavaScript runtime environment that runs on the V8 engine and executes JavaScript code outside a web browser.

ECMAScript 2015 (also known as ES6): A significant update to the ECMAScript standard introduced in 2015 that includes new syntax and features such as classes, modules, and arrow functions, greatly enhancing the capability of JavaScript.

Rollup: A JavaScript module bundler that compiles small pieces of code into something larger and more complex, such as a library or application, focusing on efficiency and speed.

Legacy Browser: An older version of a web browser that does not support newer web standards or technologies, often requiring additional scripts like polyfills to emulate missing features.

Global Environment: In JavaScript, the global environment is the context that contains all the globally accessible objects, functions, and variables.

Feature Detection: A technique used in web development to determine if certain web features are supported by the client's browser, allowing developers to conditionally load polyfills or alternative implementations.

ECMAScript Proposals: Suggestions for new features or improvements to the ECMAScript standard, which undergo a formal process of review and iteration before possibly being accepted and integrated into the standard.

TypeScript: A superset of JavaScript developed by Microsoft, which adds static types to the language. It is designed to develop large applications and transpiles to JavaScript.

Promise: An object representing the eventual completion or failure of an asynchronous operation and its resulting value, used extensively in modern JavaScript for managing asynchronous operations.

Symbol: A unique and immutable primitive value that can be used as the key of an object property, introduced in ECMAScript 2015 to help prevent name clashes between properties.

Iterator: An object that facilitates the iteration over a collection, such as an array or a string, by implementing a specific interface that returns a sequence of values.

V8: An open-source JavaScript engine developed by Google, used in Google Chrome and Node.js. It is known for its high performance and compliance with the ECMAScript standard.

Arrow Function: A concise syntax for writing function expressions in JavaScript that does not have its own `this`, `arguments`, `super`, or `new.target` bindings, which allows it to inherit them from the enclosing lexical context.

Class: A template for creating objects in JavaScript that encapsulates data and functions that operate on the data, introduced in ECMAScript 2015 to provide a more object-oriented approach to JavaScript programming.

Set: A collection of unique values in JavaScript, where each value must be unique and is a part of the standard built-in object set provided by ECMAScript 2015.

Map: An ordered collection of key-value pairs in JavaScript, where keys can be of any data type and are unique within the map, offering better performance for inserting and retrieving values compared to plain objects.

Typed Arrays: An array-like view of binary data introduced in ECMAScript 2015, which provides a mechanism for accessing raw binary data much more efficiently and with less overhead than traditional JavaScript arrays.

Async/Await: Syntactic sugar built on top of promises in JavaScript that makes asynchronous code easier to write and read. Introduced in ECMAScript 2017, it allows developers to handle asynchronous operations in a more synchronous-like fashion.

Spread Operator: A syntax in JavaScript that allows an iterable such as an array expression or string to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected.

Proxy: An object that wraps another object and intercepts operations, like reading/writing properties and others, allowing for custom behavior when these operations are performed on the proxy.

Reflect: A built-in object that provides methods for interceptable JavaScript operations, such as constructing an object, getting and setting properties. It is closely related to the Proxy mechanism and facilitates its handling of default behaviors.

Generator: A function that can stop midway and later resume its execution. Generators are useful for managing asynchronous flows and are part of the ECMAScript 2015 standard, providing an easier way to implement iterable behaviors.

Snippet from Wikipedia: Polyfill (programming)

In software development, a polyfill is code that implements a new standard feature of a deployment environment within an old version of that environment that does not natively support the feature. Most often, it refers to JavaScript code that implements an HTML5 or CSS web standard, either an established standard (supported by some browsers) on older browsers, or a proposed standard (not supported by any browsers) on existing browsers. Polyfills are also used in PHP and Python.

Polyfills allow web developers to use an API regardless of whether or not it is supported by a browser, and usually with minimal overhead. Typically they first check if a browser supports an API, and use it if available, otherwise using their own implementation. Polyfills themselves use other, more supported features, and thus different polyfills may be needed for different browsers. The term is also used as a verb: polyfilling is providing a polyfill for a feature.

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Research:

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Most Common topics:

. (navbar_core-js – see also navbar_full_stack, navbar_javascript, navbar_node, navbar_software_architecture)

Create a list of the top 30 core-js topics with no description or definitions. Sort by most common. Include NO description or definitions. Put double square brackets around each topic. Don't number them, separate each topic with only a comma and 1 space.