javascript – 将Array.map与新的Array构造函数一起使用
作者:互联网
我试图使用新的Array()构造函数与map,以创建一个单行代码,创建一个元素列表.像这样的东西:
let arr = new Array(12).map( (el, i) => {
console.log('This is never called');
return i + 1;
});
阅读docs,行为是有道理的.
Basically docs say that callback of map will be executed even for declared undefined values in array, but not for example when creating empty Arrays like the code before.
所以这应该工作:
var arr = new Array(12);
for(let i = 0; i < arr.length ; i++){
arr[i] = undefined;
}
let list = arr.map( (e, i) => {
console.log(i + 1);
return i + 1;
});
所以,我们也可以这样做:
let newArray = (length) => {
let myArray = new Array(length);
for(let i = 0; i < length; i++) myArray[i] = undefined;
return myArray;
};
console.log( newArray(12).map( (el, i) => i + 1 ) );
所以我的问题.有没有更好/漂亮的方式来做地图功能?
提前致谢!
解决方法:
您可以使用Array#from
创建一个已通过长度的数组.
Array.from({length: 12}, (e, i) => i + 1);
标签:map-function,javascript,arrays 来源: https://codeday.me/bug/20190929/1831179.html