js 数组操作

1.push /*数组末尾追加元素*/

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.push("Kiwi");
alert(fruits);
//["Banana", "Orange", "Apple", "Mango","Kiwi"]

 

2.unshift/*数组头部追加元素*/

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.unshift("Kiwi")
// ["Kiwi","Banana", "Orange", "Apple", "Mango"]

 

3.pop/*数组末尾删除元素*/

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.pop(); //["Banana", "Orange", "Apple"];

 

4.shift/*数组头部删除元素*/

 

var fruits = ["Banana", "Orange", "Apple", "Mango"];
fruits.shift(); //["Orange", "Apple", "Mango"];

 

5.concat/*合并两个数组*/

var arrFirst = [2,"蚂蚁部落"]; 
var arrSecond = ["青岛市南区","新锐公司"]; 
var newArr=arrFirst.concat(arrSecond,"蚂蚁部落一");
console.log(arrFirst);//[2, "蚂蚁部落"]
console.log(newArr);//[2, "蚂蚁部落", "青岛市南区", "新锐公司", "蚂蚁部落一"]

 

6./*map遍历数组的每一个元素，得到函数返回值组成的新数组*/

var numbers = [1,2,3,2];
var res = numbers.map(function(itme){
        return itme*2;
});
console.log(res); //[2,4,6]

 

7./*数组元素求和*/

var numbers = [1,2,3,2];

var sum = numbers.reduce(function(previous,current,index){
    return previous+current;
});
console.log(sum); //8

 

8.indexOf() //匹配的字符首次出现的索引位置

var numbers = [1,2,3,2];
//indexOf() //匹配的字符首次出现的索引位置
var index = numbers.indexOf(2);
console.log(index); //当值是-1,表示没有与之匹配的元素。或者返回相对应的索引值

 

9.与参数匹配的最后一个元素的索引

var lastindex = numbers.lastIndexOf(2);
console.log(lastindex); //与参数匹配的最后一个元素的索引

 

10//用逗号把各个元素连接起来

var numbers = [1,2,3,2];
var str = numbers.toString(); //用逗号把各个元素连接起来
console.log(str);
//1,2,3,2

 

11.用-把各个元素链接起来

var x_str = numbers.join('-');//用-把各个元素链接起来
console.log(x_str);
//1-2-3-2