数组常见函数

2016-08-07

(1) shift

删除数组第一个元素，并返回该元素，跟pop差不多

var arr=[1,2,1,3,2,3,5,6,5];
arr.shift();
console.log(arr);    //[2, 1, 3, 2, 3, 5, 6, 5]

(2) unshift

跟shift相反，往数组最前面添加元素，并返回数组新长度

var arr=[1,2,1,3,2,3,5,6,5];
arr.unshift('haha');
console.log(arr);    //["haha", 1, 2, 1, 3, 2, 3, 5, 6, 5]

(3) concat

在现有数组后面追加数组，并返回新数组，不影响现有数组

var arr=[1,2,1,3,2,3,5,6,5];
var arr1=['hahha'];
console.log(arr.concat(arr1));//[1, 2, 1, 3, 2, 3, 5, 6, 5, "hahha"]

(4) join

用指定间隔符连起来，把数组转为字符串

var arr=[1,2,1,3,2,3,5,6,5];

console.log(arr.join());   //1,2,1,3,2,3,5,6,5
console.log(arr.toString())//1,2,1,3,2,3,5,6,5toString()也可以

console.log(arr.join('*'))//1*2*1*3*2*3*5*6*5

(5) pop

删除数组最后一个元素，并返回该元素

var a =    ["aa","bb","cc"];
console.log(a.pop())    //cc
console.log(a)            //["aa", "bb"]

(6) reverse

对数组进行反排序跟，sort()一样，取第一字符ASCII值进行比较

var a =    ["aa","bb","cc"];
console.log(a.reverse());    //["cc", "bb", "aa"]
console.log(a)                    //["cc", "bb", "aa"]

(7) slice

返回数组片段

var a =    ["aa","bb","cc"];
console.log(a.slice(1,2))   //["bb"]从第一个开始到第二个，但不包含第二个
console.log(a.slice(1))        //["bb", "cc"]

数组方法小试牛刀

翻转字符串

console.log("asd".split(""))            //["a", "s", "d"]
console.log("asd".split("").reverse().join())   //d,s,a

[1,2,1,3,2,3,5,6,5] 去除重复元素

var arr=[1,2,1,3,2,3,5,6,5];
var newarr=[];
for(var i=0;i<arr.length;i++){
    if(newarr.indexOf(arr[i])==-1){
        newarr.push(arr[i]);
    }
}
console.log(newarr)//[1, 2, 3, 5, 6]

3.获取里面字面最多的字母

var str = "asdfjksdjfljsdflkjsdjf" //定义需要判断的字符串
var maxlength = 0; //用来存最大数量的变量，并初始化为0
var result; //用来接收结果

while(str != ""){
      var oldstr = str; 
      var getstr = str.substr(0,1);
    str = str.replace(new RegExp(getstr,"g"),"");
  if(oldstr.length - str.length >maxlength){
      maxlength = oldstr.length - str.length;
      result = getstr + '='+ maxlength;
  }
}
console.log(result);