黄龙

2017-04-26 23:15

一个很low的问题,forEach怎么跳出循环?

本文作者:IMWeb 黄龙 原文出处:IMWeb社区 未经同意,禁止转载

方法一: try catch

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
const _ = require('lodash');

let outArr = [];
try {
    arr.forEach(obj => {
        console.log(obj);
        if (obj < 3) {
            outArr.push(obj);
        } else {
            throw new Error('brack');
        }
    });
} catch (err) {
}

方法二:污染forEach

代码偷自https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/every

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

Array.prototype.forEach = function(fun /*, thisArg */)
  {
    'use strict';

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (typeof fun !== 'function')
        throw new TypeError();

    var thisArg = arguments.length >= 2 ? arguments[1] : void 0;
    for (var i = 0; i < len; i++)
    {
      if (i in t && fun.call(thisArg, t[i], i, t) === false)
        return false;
    }

    return true;
  };

let outArr = [];

arr.forEach(obj => {
    console.log(obj);
    if (obj < 3) {
        outArr.push(obj);
    } else {
        return false;
    }
});

方法三:用替代品

1:用lodash的_.forEach代替

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
const _ = require('lodash');
let outArr = [];
_.forEach(arr, (index, obj) => {
    console.log(obj);
    if (obj < 3) {
        outArr.push(obj);
    } else {
        return false;
    }
});

2:用every代替

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
let outArr = [];
arr.every((obj) => {
    console.log(obj);
    if (obj < 3) {
        outArr.push(obj);
    } else {
        return false;
    }

    return true;
});

3:用some代替

const arr = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
let outArr = [];
arr.some((obj) => {
    console.log(obj);
    if (obj < 3) {
        outArr.push(obj);
    } else {
        return true;
    }
});

4:for代替

5:while代替

6:do while代替

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