ES7

版本记录

• 在线规范

版本介绍

来源：在线规范 Introduction

This ECMAScript specification is the first ECMAScript edition released under Ecma TC39's new yearly release cadence and open development process. A plain-text source document was built from the ECMAScript 2015 source document to serve as the base for further development entirely on GitHub. Over the year of this standard's development, hundreds of pull requests and issues were filed representing thousands of bug fixes, editorial fixes and other improvements. Additionally, numerous software tools were developed to aid in this effort including Ecmarkup, Ecmarkdown, and Grammarkdown. This specification also includes support for a new `exponentiation operator` and adds a new method to `Array.prototype` called `includes`.

这个 ECMAScript 规范是在 Ecma TC39 新的年度发布节奏和开放开发过程下发布的第一个 ECMAScript 版本. 我们基于 ECMAScript 2015 源文件构建了一个纯文本源文件，作为完全在 GitHub 上进一步开发的基础. 在此规范制定的一年中, 有数百个请求和问题被提交，上千个 bug 修复、编辑修复和其他改进. 此外，还开发了许多软件工具来帮助这项工作，包括 Ecmarkup、Ecmarkdown 和 Grammarkdown. 此规范还包括对新的"求幂运算符"的支持，并为"Array.prototype"添加了一个新方法，称为"includes".

英文

中文

版本概要

• Array.prototype.includes
• Exponentiation operator

版本特性

Array.prototype.includes

• 参考：MDN Array.prototype.includes()
• 参考：TC39 规范

includes() 方法用来判断一个数组是否包含一个指定的值，根据情况，如果包含则返回 true，否则返回 false。

const array1 = [1, 2, 3]

console.log(array1.includes(2))
// Expected output: true

const pets = ['cat', 'dog', 'bat']

console.log(pets.includes('cat'))
// Expected output: true

console.log(pets.includes('at'))
// Expected output: false

语法

Array.prototype.includes(searchElement[, fromIndex])

幂运算符 (**)

• 参考：MDN
• 参考：TC39 规范

幂（**）运算符返回第一个操作数取第二个操作数的幂的结果。它等价于 Math.pow()，不同之处在于，它还接受 BigInt 作为操作数。

console.log(3 ** 4) // 3 * 3 * 3 * 3
// Expected output: 81
console.log(Math.pow(3, 4)) // 3 * 3 * 3 * 3
// Expected output: 81

console.log(10 ** -2)
// Expected output: 0.01

console.log(2 ** (3 ** 2))
// Expected output: 512

console.log((2 ** 3) ** 2)
// Expected output: 64