這是.sort()函數(shù)最常見的用法

//沒有函數(shù)參數(shù)，按字符編碼格式排序
var arr = [3,2,3,34,12,23,234,84,9];
arr.sort();

// 結(jié)果: 12,2,23,234,3,3,34,84,9

// 需要升序或者降序則需要傳入一個(gè)函數(shù)參數(shù)
var arr = [3,2,3,34,12,23,234,84,9];
arr.sort(function (a, b) {
    return a - b;
});
// 結(jié)果：2,3,3,9,12,23,34,84,234

// 降序
var arr = [3,2,3,34,12,23,234,84,9];
arr.sort(function (a, b) {
    return b - a;
});

但或許你還對其為什么要這么操作存有一些疑惑

我們要先搞懂往.sort()里傳入的函數(shù)的參數(shù)a，b是什么

sort()要排序就要遍歷數(shù)組，以上面的數(shù)組為例子

其中遍歷第一步的a=3、b=2，

第二步時(shí)候a=2、b=3，

第三步的時(shí)候a=3，b=34

。。。。。。。

就像你寫的冒泡排序一樣，每一個(gè)元素都會被對比到

如何排序呢？這是w3c對其的解釋：

若 a 小于 b，在排序后的數(shù)組中 a 應(yīng)該出現(xiàn)在 b 之前，則返回一個(gè)小于 0 的值。
若 a 等于 b，則返回 0。
若 a 大于b，則返回一個(gè)大于 0 的值。

也就是說，在傳入的函數(shù)里如果你想a排在b前，就return一個(gè)小于0的數(shù)

如果你想a排在b后，就return一個(gè)大于0的數(shù)

這樣，就能完成對數(shù)組元素的排序了。

清楚了原理，那么我們就可以想到一些高級的騷操作了

關(guān)于對象數(shù)組的排序：

// 按age升序排列
var users =[
{ "name": "has",   "age": 17, "height": 165 },
{ "name": "saf",   "age": 20, "height": 172 },
{ "name": "gngh",  "age": 45, "height": 182 },
{ "name": "yjerw", "age": 42, "height": 156 },
{ "name": "cvb",   "age": 22, "height": 176 },
{ "name": "wetty", "age": 32, "height": 178 },
{ "name": "aDNY",  "age": 34, "height": 175 }
     ]
users.sort(function (a, b) {
    return a.age - b.age;
});
// 結(jié)果（升序）：
/*
name:has age:17 height:165
name:saf age:20 height:172
name:cvb age:22 height:176
name:wetty age:32 height:178
name:aDNY age:34 height:175
name:yjerw age:42 height:156
name:gngh age:45 height:182
*/

// 按name排列
var users =[
{ "name": "has",   "age": 17, "height": 165 },
{ "name": "saf",   "age": 20, "height": 172 },
{ "name": "gngh",  "age": 45, "height": 182 },
{ "name": "yjerw", "age": 42, "height": 156 },
{ "name": "cvb",   "age": 22, "height": 176 },
{ "name": "wetty", "age": 32, "height": 178 },
{ "name": "aDNY",  "age": 34, "height": 175 }
     ]
var users.sort(function (a, b) {
    return a.name - b.name;
});
// 結(jié)果：
/*
name:aDNY age:34 height:175
name:cvb age:22 height:176
name:gngh age:45 height:182
name:has age:17 height:165
name:saf age:20 height:172
name:wetty age:32 height:178
name:yjerw age:42 height:156
*/

// 按布爾值排列
var users=[
{ "name": "has",   "age": 17, "height": 165, "state": true},
{ "name": "saf",   "age": 20, "height": 172, "state": false},
{ "name": "gngh",  "age": 45, "height": 182, "state": false },
{ "name": "yjerw", "age": 42, "height": 156, "state": true },
{ "name": "cvb",   "age": 22, "height": 176, "state": false },
{ "name": "wetty", "age": 32, "height": 178, "state": true },
{ "name": "aDNY",  "age": 34, "height": 175, "state": false }
     ]
users.sort(function (a, b) {
    return b.state- a.state;
});
//眾所周知，true - false = 1 
//結(jié)果
/*
[
  { name: "has", age: 17, height: 165, state: true },
  { name: "yjerw", age: 42, height: 156, state: true },
  { name: "wetty", age: 32, height: 178, state: true },
  { name: "saf", age: 20, height: 172, state: false },
  { name: "gngh", age: 45, height: 182, state: false },
  { name: "cvb", age: 22, height: 176, state: false },
  { name: "aDNY", age: 34, height: 175, state: false }
]
*/

總結(jié)

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