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• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

unshift() method adds one or more elements to the beginning of an array and returns the new length of the array.

句法

arr.unshift(element1[, ...[, elementN]])
					

参数

element N

The elements to add to the front of the arr .

返回值

The new length property of the object upon which the method was called.

描述

unshift method inserts the given values to the beginning of an array-like object.

unshift is intentionally generic. This method can be called or applied to objects resembling arrays. Objects which do not contain a length property—reflecting the last in a series of consecutive, zero-based numerical properties—may not behave in any meaningful manner.

Please note that, if multiple elements are passed as parameters, they're inserted in chunk at the beginning of the object, in the exact same order they were passed as parameters. Hence, calling unshift with n arguments once , or calling it n times with 1 argument (with a loop, for example), don't yield the same results.

See example:

let arr = [4, 5, 6]
arr.unshift(1, 2, 3)
console.log(arr);
// [1, 2, 3, 4, 5, 6]
arr = [4, 5, 6] // resetting the array
arr.unshift(1)
arr.unshift(2)
arr.unshift(3)
console.log(arr)
// [3, 2, 1, 4, 5, 6]
					

范例

Using unshift

let arr = [1, 2]
arr.unshift(0)               // result of the call is 3, which is the new array length
// arr is [0, 1, 2]
arr.unshift(-2, -1)          // the new array length is 5
// arr is [-2, -1, 0, 1, 2]
arr.unshift([-4, -3])        // the new array length is 6
// arr is [[-4, -3], -2, -1, 0, 1, 2]
arr.unshift([-7, -6], [-5])  // the new array length is 8
// arr is [ [-7, -6], [-5], [-4, -3], -2, -1, 0, 1, 2 ]
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Array.prototype.unshift' in that specification.

浏览器兼容性

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
unshift	Chrome 1	Edge 12	Firefox 1	IE 5.5	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100

图例

完整支持

完整支持

另请参阅

• Array.prototype.push()
• Array.prototype.pop()
• Array.prototype.shift()
• Array.prototype.concat()

元数据

• 最后修改： May 6, 2020

相关话题

1. 标准内置对象
2. Array
3. 特性
   1. Array.prototype.length
   2. Array.prototype[@@unscopables]
4. 方法
   1. Array.from()
   2. Array.isArray()
   3. Array.of()
   4. Array.prototype.concat()
   5. Array.prototype.copyWithin()
   6. Array.prototype.entries()
   7. Array.prototype.every()
   8. Array.prototype.fill()
   9. Array.prototype.filter()
   10. Array.prototype.find()
   11. Array.prototype.findIndex()
   12. Array.prototype.flat()
   13. Array.prototype.flatMap()
   14. Array.prototype.forEach()
   15. Array.prototype.includes()
   16. Array.prototype.indexOf()
   17. Array.prototype.join()
   18. Array.prototype.keys()
   19. Array.prototype.lastIndexOf()
   20. Array.prototype.map()
   21. Array.prototype.pop()
   22. Array.prototype.push()
   23. Array.prototype.reduce()
   24. Array.prototype.reduceRight()
   25. Array.prototype.reverse()
   26. Array.prototype.shift()
   27. Array.prototype.slice()
   28. Array.prototype.some()
   29. Array.prototype.sort()
   30. Array.prototype.splice()
   31. Array.prototype.toLocaleString()
   32. Array.prototype.toSource()
   33. Array.prototype.toString()
   34. Array.prototype.unshift()
   35. Array.prototype.values()
   36. Array.prototype[@@iterator]()
   37. get Array[@@species]
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
9. Object
10. 特性
    1. Object.prototype.__proto__
    2. Object.prototype.constructor
11. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()