javascript创建给定大小的空数组

in javascript how would I create an empty array of a given size

在javascript中如何创建给定大小的空数组

Psuedo code:

X = 3;
createarray(myarray, X, "");

output:

   myarray = ["","",""]

7 个解决方案

#1

var arr = new Array(5);
console.log(arr.length) // 5

#2

1) To create new array which, you cannot iterate over, you can use array constructor:

1)要创建新的数组,你不能迭代,你可以使用数组构造函数:

Array(100) or new Array(100)

数组(100)或新数组(100)

2) You can create new array, which can be iterated over like below:

2)你可以创建新的数组,可以迭代如下:

a) All JavaScript versions

a)所有JavaScript版本

• Array.apply: Array.apply(null, Array(100))

Array.apply:Array.apply(null,Array(100))

b) From ES6 JavaScript version

b)来自ES6 JavaScript版本

• Destructuring operator: [...Array(100)]

解构运算符:[...数组(100)]

• Array.prototype.fill Array(100).fill(undefined)
• Array.prototype.from Array.from({ length: 100 })

Array.prototype.from Array.from({length:100})

You can map over these arrays like below.

您可以映射这些数组,如下所示。

• Array(4).fill(null).map((u, i) => i) [0, 1, 2, 3]

  数组(4).fill(null).map((u,i)=> i)[0,1,2,3]

• [...Array(4)].map((u, i) => i) [0, 1, 2, 3]

  [...数组(4)]。map((u,i)=> i)[0,1,2,3]

• Array.apply(null, Array(4)).map((u, i) => i) [0, 1, 2, 3]

  Array.apply(null,Array(4))。map((u,i)=> i)[0,1,2,3]

• Array.from({ length: 4 }).map((u, i) => i) [0, 1, 2, 3]

  Array.from({length:4})。map((u,i)=> i)[0,1,2,3]

#3

We use Array.from({length: 500}) in 2017.

我们在2017年使用Array.from({length:500})。

#4

Try using while loop, Array.prototype.push()

尝试使用while循环,Array.prototype.push()

var myArray = [], X = 3;
while (myArray.length < X) {
  myArray.push("")
}

Alternatively, using Array.prototype.fill()

或者,使用Array.prototype.fill()

var myArray = Array(3).fill("");

#5

If you want an empty array of undefined elements, you could simply do

如果你想要一个空数组的未定义元素,你可以简单地做

var whatever = new Array(5);

this would give you

这会给你

[undefined, undefined, undefined, undefined, undefined]

and then if you wanted it to be filled with empty strings, you could do

如果你想要用空字符串填充它,你可以做到

whatever.fill('');

which would give you

这会给你

["", "", "", "", ""]

And if you want to do it in one line:

如果你想在一行中做到这一点:

var whatever = Array(5).fill('');

#6

In 2018 and thenceforth we shall use [...Array(500)] to that end.

在2018年,从那时起我们将[... Array(500)]用于此目的。

#7

I would do this:

我会这样做:

function emptyArray(length){
  var a = [];
  for(var i=0,l=length; i<l; i++){
    a.push('');
  }
  return a;
}
var empty10 = emptyArray(10);

if you want empty Strings, otherwise

如果你想要空字符串,否则

var empty10 = new Array(10);

will make a truly empty Array.

将制作一个真正空的数组。