js中基本类型操作-----数组基本操作、字符串操作、json操作

push() js数组插入

var a = [1,2,3];
var b = a.push('4','5');
console.log(a); //[1,2,3,4,5]
console.log(b); //5

pop()返回数组最后一个元素

var a = [1,2,3];
var b = a.pop();
console.log(a); //[1,2]
console.log(b); //3

concat链接两个或者多个数组---不改变原有数组，只返回新数组

var a = [1,2,3];
var b = a.concat(6,7);
console.log(a); //[1,2,3]
console.log(b); //[1,2,3,6,7]

join（str）把数组的所有元素用str隔开返回字符串

var a = [1,2,3]
var b = a.join('|');
console.log(a); //[1,2,3]
console.log(b); //"1|2|3"

toString()返回字符串

var a = [1,2,3,4,5];
var b = a.toString();
console.log(a); //[1,2,3,4,5]
console.log(b); //"1,2,3,4,5"

revierse()反转数组中元素顺序，改变原有数组

var a = [1,2,3,4,5];
var b = a.reverse();
console.log(a); //[5,4,3,2,1]
console.log(b); //[5,4,3,2,1]

shift()删除并返回数组的第一个元素

var a = [1,2,3];
var b = a.shift();
console.log(a); //[2,3]
console.log(b); //1

slice(start,end)从已有的数组中返回选定的元素不改变原有数组

var a = [1,2,3,4,5];
var b = a.slice(0,-1);
var c = a.slice(1,3);
var d = a.slice(1);
var e = a.slice(2,-2);
var f = a.slice(3,1);
console.log(a); //[1,2,3,4,5]
console.log(b); //[1,2,3,4]
console.log(c); //[2,3]
console.log(d); //[2,3,4,5]
console.log(e); //[3]
console.log(f); //[]

splice(start,deletecount,val1,val2,...)改变原有数组

从一个数组中移除一个或多个元素，并在该位置插入新元素，返回所移除的元素

var a = [1,2,3,4,5];
var b = a.splice(2,2,7,8);
console.log(a); //[1,2,7,8,5]
console.log(b); //[3,4]

sort(func)

var a = [1,2,10,3];
var b = a.sort();
console.log(a); //[1,10,2,3]
console.log(b); //[1,10,2,3]
var num = function(x,y) {
  return x - y;
}
var c = a.sort(num);
console.log(a); //[1,2,3,10]
console.log(c); //[1,2,3,10]

js数组清空3种方式

var ary = [1,2,3,4];ary.splice(0,ary.length);console.log(ary); // 输出 []，空数组，即被清空了

int[] ary = {1,2,3,4};ary=[];

int[] ary = {1,2,3,4};ary.length = 0;