数组的简单总结

2016-12-20 本文已影响10人 Hunter_Gu

定义数组：

var arr1 = new Array(5);//长度为5的空数组
var arr2 = new Array(1,5);//[1,5]

var arr1 = [];
var arr2 = [1,2,3,4];

数组的长度 arr.length

数组的方法：

var arr = [1,2,3];
arr[3] = 4;//添加
arr;//[1,2,3,4]
delete a[0];//删除
arr;//[undefined,2,3,4]
arr[1] = 5;//修改
arr;//[undefined,5,3,4]

var arr = [1,2,3,4];
arr.pop();//4
arr;//[1,2,3]

var arr = [1,2,3,4];
arr.push(5,6);//6
/*
arr[arr.length] = 5;
arr[arr.length] = 6;
*/
arr;//[1,2,3,4,5,6]

var arr = [1,2,3,4];
arr.shift();//1
arr;//[2,3,4]

var arr = [1,2,3,4];
arr.unshift(-1,0);//6
/*
arr[0] = 0;
arr[0] = -1;
*/
arr;//[-1,0,1,2,3,4]

var arr = [1,2,3,4,5];
arr.splice(1,3);//[2,3,4]
arr;//[1,5]

var arr = [1,2,3,4,5];
arr.splice(1,0,3);//[]
arr;//[1, 3, 2, 3, 4, 5]

var arr = [1,2,3,4];
arr.join('-');//'1-2-3-4'
arr.join('');'1234'

var arr = [1,2,3,4,5];
arr.slice(1,3);//[2,3]
arr;//[1,2,3,4,5]

var arr1 = [1,2,3,4],
    arr2 = [5,6,7];
arr1.concat(arr2);//[1,2,3,4,5,6,7]

var arr = [1,2,3];
arr.reverse();//[3,2,1]
arr;//[3,2,1]

var arr = [1,2,31,100,256];
arr.sort();//[1,100,2,256,31]

可以重写该方法

var arr = [1,2,31,100,256];
arr.sort(function(a,b){
    return a-b;//a-b>0,则调换
});

ES5中数组的拓展

var arr = [];
Array.isArray(arr);//true;
/*
//满足这两点的，也一定是数组
typeof arr;//'object'
arr instanceof Array;//true
*/

var arr = [1,2,3,3,2,1];
arr.indexOf(2);//1

var arr = [1,2,3,3,2,1];
arr.lastIndexOf(2);//4

var arr = [1,2,3,4,5];
arr.forEach(function(ele,index,array){
    array[index] = ele +1;
});
arr;//[2,3,4,5,6]

var arr = [1,2,3,4,5];
arr.every(function(e,i,a){
   return e > 0;
});//true

var arr = [1,2,3,4,5];
arr.some(function(e,i,a){
    return e > 3;
});//true

var arr = [1,2,3];
/*map基于原数组操作*/
arr.map(function(e){
    return e*e;
});//[1,4,9]
arr;//[1,2,3]

var arr = [1,2,3,4,5];
arr.filter(function(ele){
    return ele > 2;
});[3,4,5]
arr;//[1,2,3,4,5]