【js基础】数组相关操作函数

<script type="text/javascript">//数组创建var arr = new Array(1,2,3);var arr = [1,2,3,4];//数组长度var length = arr.length;//添加元素arr.push("red","yellow");//在最后推入两项 arr.concat("red"); //先拷贝数组，然后同上function insert(arr, item, index) { //在arr的index处添加item  var newArr=arr.slice(0);   newArr.splice(index,0,item);   return newArr; } //删除元素function truncate(arr) { //删除最后一个  var newArr = arr.concat();   newArr.pop();   return newArr; } function curtail(arr) { //删除第一个  var newArr = arr.concat();   newArr.shift();   return newArr; }function curtail(arr) { //删除第一个  return arr.slice(1); } //数组合并arr1.concat(arr2); //数组去重Array.prototype.unique3 = function(){ var res = []; var json = {}; for(var i = 0; i < this.length; i++){  if(!json[this[i]]){   res.push(this[i]);   json[this[i]] = 1;  } } return res;}var arr = [112,112,34,'你好',112,112,34,'你好','str','str1'];alert(arr.unique3());//数组转字符串并用-连接var a, b;a = new Array(0,1,2,3,4);b = a.join("-");//字符串转数组var s = "abc,abcd,aaa";ss = s.split(",");// 在每个逗号(,)处进行分解。//判断元素是否在数组中function contains(arr, obj) {      var i = arr.length;      while (i--) {          if (arr[i] === obj) {              return true;          }      }      return false;  }</script>