Javascript |设置数组的所有值

Code

码

var cool = new Array(3);
cool[setAll] = 42; //cool[setAll] is just a pseudo selector..
alert(cool);

Result

结果

A alert message:

提醒消息：

42,42,42

How do I change/set all values of an array to a specific value?

如何将数组的所有值更改/设置为特定值？

7 个解决方案

#1

There's no built-in way, you'll have to loop over all of them:

没有内置方式，你必须遍历所有这些：

function setAll(a, v) {
    var i, n = a.length;
    for (i = 0; i < n; ++i) {
        a[i] = v;
    }
}

http://jsfiddle.net/alnitak/xG88A/

If you really want, do this:

如果你真的想要，请这样做：

Array.prototype.setAll = function(v) {
    var i, n = this.length;
    for (i = 0; i < n; ++i) {
        this[i] = v;
    }
};

and then you could actually do cool.setAll(42) (see http://jsfiddle.net/alnitak/ee3hb/).

然后你实际上可以做cool.setAll（42）（参见http://jsfiddle.net/alnitak/ee3hb/）。

Some people frown upon extending the prototype of built-in types, though.

不过，有些人不屑于扩展内置类型的原型。

EDIT ES5 introduced a way to safely extend both Object.prototype and Array.prototype without breaking for ... in ... enumeration:

编辑ES5引入了一种安全地扩展Object.prototype和Array.prototype的方法，而不会破坏... in ...枚举：

Object.defineProperty(Array.prototype, 'setAll', {
    value: function(v) {
        ...
    }
});

EDIT 2 In ES6 draft there's also now Array.prototype.fill, usage cool.fill(42)

编辑2在ES6草案中，现在还有Array.prototype.fill，用法cool.fill（42）

#2

map is the most logical solution for this problem.

map是解决此问题的最合理的解决方案。

let xs = [1, 2, 3];
xs = xs.map(x => 42);
xs // -> [42, 42, 42]

However, if there is a chance that the array is sparse, you'll need to use for or, even better, for .. of.

但是，如果阵列有可能是稀疏的，那么你需要使用for或者甚至更好的。

See:

看到：

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/map
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/map
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of

#3

The ES6 approach is very clean. So first you initialize an array of x length, and then call the fill method on it.

ES6的方法很干净。首先，初始化一个x长度的数组，然后在其上调用fill方法。

let arr = new Array(3).fill(9)

this will create an array with 3 elements like:

这将创建一个包含3个元素的数组，如：

[9, 9, 9]

#4

Use a for loop and set each one in turn.

使用for循环并依次设置每个循环。

#5

The other answers are Ok, but a while loop seems more appropriate:

其他答案都是好的，但是一个while循环似乎更合适：

function setAll(array, value) {
  var i = array.length;
  while (i--) {
    array[i] = value;
  }
}

A more creative version:

更具创意的版本：

function replaceAll(array, value) {
  var re = new RegExp(value, 'g');
  return new Array(++array.length).toString().replace(/,/g, value).match(re);
}

May not work everywhere though. :-)

虽然可能无处不在。 :-)

#6

One solution using native code is this:

使用本机代码的一个解决方案是：

var cool = new Array(3);
cool.fill(42);

#7

-1

Try this:

尝试这个：

for(var i in array) array[i]=fixedValue;

#1