前端web学习--js中数组的操作方法
回顾知识点，js中数组的操作方法
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shift,unshift,pop,push,concat,splice,slice,reverse,sort,join
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// shift():删除数组第一个元素,并返回该元素的值,改变原数组;
// unshift():添加一个元素到数组首位,返回新数组的长度,改变原数组;
// pop():删除数组最后一个元素,并返回该元素的的值,改变原数组;
// push():添加一个元素到数组末位,返回新数组的长度,改变原数组;
// concat([被连接的数组]):连接两个数组,组成一个新数组,不改变原数组;
// splice(start,length,"新元素1","新元素2"):在原数组中截取某一段并在该位置添加新元素,返回的是删除的元素所组成的新数组,改变原数组
// slice(start,end):截取一段数组,返回截取的元素组成的新数组，不改变原数组
// join("间隔符，默认为逗号"):使用间隔符将数组改变为字符串,默认间隔符是逗号(，),可用于将数组转化为字符串.不改变原数组;
// reverse():反序,返回的是改变顺序后的新数组,改变原数组
// sort():排序,按照ascll字符编码排序,返回排序后的新数组,改变原数组;
var a = ["sdf","s","sa","a","f","fe","fs",654,89,65189]
var a1 = a.sort();
console.log(a1) // [65189,654,89,"a","f","fe","fs","s","sa","sdf"]
console.log(a) // [65189,654,89,"a","f","fe","fs","s","sa","sdf"]
var a2 = a.reverse();
console.log(a2) // ["sdf","sa","s","fs","fe","f","a",89,654,65189]
console.log(a) // ["sdf","sa","s","fs","fe","f","a",89,654,65189]
var a3 = a.pop();
console.log(a3) // 65189
console.log(a) // ["sdf","sa","s","fs","fe","f","a",89,654]
var a4 = a.push("新添加第一次");
console.log(a4) // 10
console.log(a) // ["sdf","sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a5 = a.shift();
console.log(a5) // sdf
console.log(a) // ["sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a6 = a.unshift("添加2次");
console.log(a6) // 10
console.log(a) // ["添加2次","sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a7 = a.concat("连接111");
console.log(a7) // ["添加2次","sa","s","fs","fe","f","a",89,654,"新添加第一次","连接111"]
console.log(a) // ["添加2次","sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a8 = a.join();
console.log(a8) // 添加2次,sa,s,fs,fe,f,a,89,654,新添加第一次
console.log(a) // ["添加2次","sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a9 = a.slice(2,5);
console.log(a9) // ["s","fs","fe"]
console.log(a) // ["添加2次","sa","s","fs","fe","f","a",89,654,"新添加第一次"]
var a10 = a.splice(2,5,"添加222","添加333")
console.log(a10)// ["s","fs","fe","f","a"]
console.log(a) // ["添加2次","sa","添加222","添加333",89,654,"新添加第一次"]
// shift 删除数组的第一项 返回值是被删除的元素
// a.shift();
// console.log(a.shift())
// console.log(a)
// unshift 添加到数组的第一项 返回的是新数组的长度
// console.log(a.unshift("84s"));
// console.log(a)
// pop 删除数组的最后一项元素， 并返回被删除的元素
// console.log(a.pop());
// console.log(a)
// push 向数组最后添加一项，返回的是新数组的长度
// console.log(a.push("5sd5f2"));
// console.log(a)
// slice 截取数组某一部分，返回的是被截取的部分组成的新数组,不改变原数组
// console.log(a.slice(2,4));
// console.log(a)
// splice 截取一部分并可以添加,改变原数组,返回的是被截取的部分组成的新数组
// console.log(a.splice(2,3,"5416k","5154"))
// console.log(a);
// concat
// console.log(a.concat([111111]))
// console.log(a)
// join
// console.log(a.join())
// console.log(a)
// reverse
// console.log(a.reverse())
// console.log(a)
// sort
// console.log(a.sort())
// console.log(a)
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