Javascript | 设置数组的所有值
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/5802762/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Javascript | Set all values of an array
提问by Tomkay
Code
代码
var cool = new Array(3);
cool[setAll] = 42; //cool[setAll] is just a pseudo selector..
alert(cool);
Result
结果
A alert message:
一条警告消息：
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？
回答by Alnitak
There's no built-in way, you'll have to loop over all of them:
没有内置方法，您必须遍历所有方法：
function setAll(a, v) {
var i, n = a.length;
for (i = 0; i < n; ++i) {
a[i] = v;
}
}
http://jsfiddle.net/alnitak/xG88A/
http://jsfiddle.net/alnitak/xG88A/
If you reallywant, do this:
如果您真的想要，请执行以下操作：
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)（见http://jsfiddle.net/alnitak/ee3hb/）。
Some people frown upon extending the prototype of built-in types, though.
不过，有些人不赞成扩展内置类型的原型。
EDITES5 introduced a way to safely extend both Object.prototypeand Array.prototypewithout breaking for ... in ...enumeration:
编辑ES5引入的方式安全地扩展双方Object.prototype并Array.prototype没有打破for ... in ...列举：
Object.defineProperty(Array.prototype, 'setAll', {
value: function(v) {
...
}
});
EDIT 2In 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)
回答by Faris Zacina
The ES6 approach is very clean. So first you initialize an array of x length, and then call the fillmethod on it.
ES6 方法非常干净。所以首先你初始化一个 x 长度的数组，然后调用fill它的方法。
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，例如：
[9, 9, 9]
回答by mustafa.0x
mapis the most logical solution for this problem.
map是这个问题最合乎逻辑的解决方案。
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 foror, even better, for .. of.
但是，如果数组有可能是稀疏的，您将需要使用，for或者更好的是，for .. of.
See:
看：
回答by Quentin
Use a forloop and set each one in turn.
使用for循环并依次设置每个循环。
回答by Сергей Язев
Actually, you can use this perfect approach:
实际上，您可以使用这种完美的方法：
let arr = Array.apply(null, Array(5)).map(() => 0);
// [0, 0, 0, 0, 0]
This code will create array and fill it with zeroes. Or just:
此代码将创建数组并用零填充它。要不就：
let arr = new Array(5).fill(0)
回答by Сергей Язев
It's 2019 and you should be using this:
现在是 2019 年，你应该使用这个：
let arr = [...Array(20)].fill(10)
let arr = [...Array(20)].fill(10)
So basically 20is the lengthor a new instantiated Array.
所以基本上20是length或者一个新的实例化了Array。
回答by RobG
The other answers are Ok, but a while loop seems more appropriate:
其他答案是好的，但 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:
更有创意的版本：
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. :-)
虽然可能无法在任何地方工作。:-)
