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What's New in JavaScript

This document lists new features in JavaScript that are supported in both Internet Explorer 11, Windows Store, and Windows Phone Store apps.

To find out which JavaScript elements are supported in Internet Explorer 11 but deprecated in Windows Store apps, see JavaScript Version Information.

Important note Important

For information about how to create Windows Store and Windows Phone Store apps using JavaScript, including information about the Visual Studio JavaScript editor and other features, see Develop Windows Store apps using Visual Studio 2013.

You can use the new let and const keywords to declare variables whose scope is limited to the block in which they're declared. See let Statement (JavaScript) and const Statement (JavaScript).

You can create a collection of unique objects by using the Set Object (JavaScript) object, and you can create a collection of key/value pairs by using Map Object (JavaScript) or WeakMap Object (JavaScript).

Locale-specific date and time formatting, number formatting, and comparisons are provided through the Internationalization API, which conforms to the ECMAScript Internationalization API Specification. See Intl.DateTimeFormat Object (JavaScript), Intl.NumberFormat Object (JavaScript), and Intl.Collator Object (JavaScript).

You can use the __proto__ property to set the prototype for user-defined objects, intrinsic objects, and functions. See __proto__ Property (Object) (JavaScript).

A new typed array, Uint8ClampedArray Object (JavaScript), provides support for typed arrays that consist of 8-bit unsigned integers with values clamped to the range 0-255. In addition, the ArrayBuffer object now supports the slice Method (ArrayBuffer) and ArrayBuffer.isView Function (ArrayBuffer).

You can instrument your code to provide the debugger with tracing information for your asynchronous functions. This information can be used by tools such as Visual Studio to provide better debugging information in the Call Stack window and the Tasks window. For more information, see Debug Object (JavaScript).

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