The set() method adds a new element with a specified key and value to a WeakMap object.

ECMAScript6 JavaScript Method Prototype WeakMap

The add() method appends a new object to the end of a WeakSet object.

ECMAScript6 JavaScript Method Prototype WeakSet

The delete() method removes the specified element from a WeakSet object.

ECMAScript6 JavaScript Method Prototype WeakSet

The has() method returns a boolean indicating whether an object exists in a WeakSet or not.

ECMAScript6 JavaScript Method Prototype WeakSet

One addition of ECMAScript 2015 (ES6) is not new syntax or a new built-in, but a protocol. This protocol can be implemented by any object respecting some conventions.

ECMAScript6 Intermediate Iterable Iterator JavaScript

The destructuring assignment syntax is a JavaScript expression that makes it possible to extract data from arrays or objects into distinct variables.

Destructuring ECMAScript6 JavaScript Operator operator

The spread syntax allows an expression to be expanded in places where multiple arguments (for function calls) or multiple elements (for array literals) or multiple variables  (for destructuring assignment) are expected.

ECMAScript6 Iterator JavaScript operator Operator

This declaration creates a constant that can be either global or local to the function in which it is declared. An initializer for a constant is required; that is, you must specify its value in the same statement in which it's declared (which makes sense, given that it can't be changed later).

constants ECMAScript6 JavaScript Reference Statement

The function* declaration (function keyword followed by an asterisk) defines a generator function, which returns a Generator object.

ECMAScript6 Function Iterator JavaScript Statement

JavaScript classes are introduced in ECMAScript 6 are syntactical sugar over JavaScript's existing prototype-based inheritance. The class syntax is not introducing a new object-oriented inheritance model to JavaScript. JavaScript classes provide a much simpler and clearer syntax to create objects and deal with inheritance.

Classes Constructors ECMAScript6 Inheritance Intermediate JavaScript

The initial value of the @@iterator property is the same function object as the initial value of the values() property.

Array ECMAScript6 Iterator JavaScript Method Prototype Reference

The copyWithin() method shallow copies part of an array to another location in the same array and returns it, without modifying its size.

Array ECMAScript6 JavaScript Method polyfill Prototype

The entries() method returns a new Array Iterator object that contains the key/value pairs for each index in the array.

Array ECMAScript6 Iterator JavaScript Method Prototype

The every() method tests whether all elements in the array pass the test implemented by the provided function.

Array ECMAScript5 JavaScript Method polyfill Prototype

The fill() method fills all the elements of an array from a start index to an end index with a static value.

Array ECMAScript6 JavaScript Method polyfill Prototype

The filter() method creates a new array with all elements that pass the test implemented by the provided function.

Array ECMAScript5 JavaScript Method polyfill Prototype Reference

The findIndex() method returns an index in the array, if an element in the array satisfies the provided testing function. Otherwise -1 is returned.

Array ECMAScript6 JavaScript Method polyfill Prototype

The forEach() method executes a provided function once per array element.

Array ECMAScript5 JavaScript Method Prototype Reference

The keys() method returns a new Array Iterator that contains the keys for each index in the array.

Array ECMAScript6 Iterator JavaScript Method Prototype

The lastIndexOf() method returns the last index at which a given element can be found in the array, or -1 if it is not present. The array is searched backwards, starting at fromIndex.

Array ECMAScript5 JavaScript Method polyfill Prototype