join
数组元素拼接，默认以
,作为连接符号，也可自定义。
示例：
var items = [1,2,3];
console.log(items.join());
//output: 1,2,3
var items = [1,2,3];
console.log(items.join("---"));
//output: 1---2---3
concat
数组合并。
示例
var items = [1,2,3];
var newItems1 = items.concat(4,5);
console.log(newItems1);
//output: [1,2,3,4,5]
var newItems2 = items.concat([4,5]);
console.log(newItems2);
//output: [1,2,3,4,5]
var newItems3 = items.concat([4,[5,6]]);
console.log(newItems3);
//output: [1,2,3,4,[5,6]]
var department_a = [
{name: "test"},
{name: "dev"},
{name: "opt"}
];
var department_b = [
{name: "marketing"},
{name: "fanciance"}
];
department_a.concat(department_b).forEach(function(e){
console.log(e.name);
});
/*output:
test
dev
opt
marketing
fanciance
*/
indexof
读取数组元素位置，返回元素下标值；元素不存在时返回
-1
示例
var names = ["brj","mlx","cc","xb","mm"];
console.log(names.indexOf("cc"));
//output: 2
console.log(names.indexOf("lx"));
//output: -1
var brj = {name: "brj"};
var mlx = {name: "mlx"};
var cc = {name: "cc"};
var family = [
brj,
mlx,
cc
];
console.log(family.indexOf(brj));
//output: 0
var whiteList = [".css",".js"];
var files = [
{file: "assets/a.js"},
{file: "assets/a.css"},
{file: "assets/index.html"}
];
files.filter(function(e){
var ext = "." + e.file.split(".")[1];
return whiteList.indexOf(ext) > -1;
}).forEach(function(f){
console.log(f.file);
});
/*output:
assets/a.js
assets/a.css
*/
Sort
sort 默认是按照字符顺序排列的，即使数字数组也是先转为字符串然后再排序的.并且sort会改变原数组的值
示例
var numbers = [10,30,2]
numbers.sort();
console.log(numbers);
//output: [10,2,30]
/* 按数值大小排序 */
var numbers = [10,30,2]
numbers.sort(function(a,b){
return b - a;
});
console.log(numbers);
//output: [30,10,2]
/*sort by string length*/
var titles = ["How are you?","logs is not empty,you know?","Hi","o"]
titles.sort(function(a,b){
return b.length - a.length
});
console.log(titles);
//output: ["logs is not empty,you know?","How are you?","Hi","o"]
/*sort by hash value (sort by date)*/
var lessons = [{
title: "drive",
viewers: 20,
settings:{
last_active_date: "2016-02-22 09:53:02 +0800"
}
}, {
title: "drink",
viewers: 26,
settings:{
last_active_date: "2016-02-25 09:23:08 +0800"
}
}, {
title: "drag",
viewers: 3,
settings:{
last_active_date: "2016-02-24 09:35:08 +0800"
}
}];
var list = lessons.sort(function(a, b) {
/*FireFox下Date.parse(a.settings.last_active_date) 输出结果为：NaN*/
var a_date = Date.parse(a.settings.last_active_date);
var b_date = Date.parse(b.settings.last_active_date);
return a_date - b_date;
});
list.map(function(l) {
return l.title + "(" + l.viewers + ")"
}).join("|");
console.log(list);
//output: drive(20)|drag(3)|drink(26) (Chrome 下的测试结果)
reduce
简单理解为聚合函数
示例
var arr = [3,1,2]
var total = arr.reduce(function(a,b){return a+b});
console.log(total);
//output: 6
