js split()、join()、substring()、flat(Infinity)的使用

split() 方法用于把一个字符串分割成字符串数组

var str = "I love you too";

var aa = str.split(" ");
console.log(aa); //["I", "love", "you", "too"]

join() 方法用于把数组中的所有元素放入一个字符串

var str = ["I", "love", "you", "too"]

var aa = str.join(" ");
console.log(aa); // I love you too

substring(0, 5) js怎样截取字符串后几位以及截取字符串前几位

想要截取字符串前几位与后几位， 主要代码如下

//截取字符串前几位

var disName = '开心一族漂亮家园';
var shortName = disName.substring(0, 5);
console.log(shortName); //打印结果：开心一族漂

//截取字符串后几位

var disName = '开心一族漂亮家园';
var disLength = disName.length;
var shortName = disName.substring(disLength - 2, disLength);
console.log(shortName); //打印结果：家园

flat(Infinity) 数组扁平化

const prov = [{
        "initial": "A",
        "cells": [{
                "code": "34",
                "name": "安徽省",
                "py": "an"
            },
            {
                "code": "853",
                "name": "澳门特别行政区",
                "py": "ao"
            }
        ]
    },
    {
        "initial": "B",
        "cells": [{
            "code": "11",
            "name": "北京市",
            "py": "bei"
        }]
    },
]

function getProvinceData(array) {
    let tempt = array.map(item => item.cells)
    return tempt.flat(Infinity)
}

function compare(arg) {
    return function(a, b) {
        return a[arg] - b[arg];
    }
}
const alphabet = getProvinceData(prov).sort(compare('code'))
console.log(alphabet)//[{"code":"11","name":"北京市","py":"bei"},{"code":"34","name":"安徽省","py":"an"},{"code":"853","name":"澳门特别行政区","py":"ao"}]