JS Array Intermediate + Advanced tips

This paper introduces some methods to compare advanced JS arrays:

reverse: array inversion;

Join: (parameter) stitching an array into a string with a parameter as a connector;

Instance:

var arr=[];

arr[3]= "haha";

Console.log (Arr.join ("a"));//output: Aaahaha; ARR[3] actually defines an array length of 4 and the first 3 items are undifided, so join ("a") is: null +a+ NULL + a null + A + haha

To implement string inversion with the string split method:

String.prototype.reverse=function () {
Return This.split (""). Reverse (). Join ("");
}

To generate a cumulative array quickly:

for (var i = 1, arr=[]; Arr.push (i++) <10;);

Console.log (arr);//[1,2,3,4,5,6,7,8,9,10]//change 10 to the desired number

Array sorting:

var arr=[1,13,500,70]

Maximum value: Math.max.apply (Null,arr);//500

Minimum value: Math.min.apply (Null,arr); 1

Sort: from large to small : Arr.sort ((A, b) =>b-a) or Arr.sort (function (A, b) {return b-a});

　　　from small to large :: Arr.sort ((A, b) =>a-b) or Arr.sort (function (A, b) {return-A-b});

　　　Random sort arr.sort (function () {return math.random ()-0.5});

　　double standard sort :

Example 1: Require arr to be sorted by num size, if NUM is the same, in the new Order of time

var arr= [
{name: ' QQQ ', num:2,time: ' 2015-06-08 13:44:18 '},
{name: ' www ', num:3,time: ' 2015-06-08 13:44:18 '},
{name: ' eee ', num:4,time: ' 2015-06-07 13:40:18 '},
{name: ' RRR ', Num:4,time: ' 2015-06-08 13:44:18 '},
{name: ' yyy ', num:6,time: ' 2015-06-07 13:40:18 '},
];

Arr.sort (A, b) =>a.num==b.num? Date.parse (b.time)-date.parse (a.time): B.num-a.num)

Example 2: Requirements: Sort arr by the number in each item from small to large

var arr=["That you dasda1222", "Hahaha Das32dasdsa", "Nani 8888dasdsadas", "aaa333"];

Arr.sort (b) =>a.match (/\d/)-B.match (/\d/))

or Arr.sort (function (A, b) {return A.match (/\d/)-B.match (/\d/)})

Array de-weight:

1 Basic version:　

Array.prototype.unique = function () {

Creates a new temporary array to hold the output results
var n = [];

for (var i = 0; i < this.length; i++) {
If the element I of the current array has been saved into a temporary array, skip it, or push the current item into the temporary array
if (N.indexof (this[i]) = =-1) n.push (This[i]);
}
return n;
}

2 Efficient version

Array.prototype.unique = function () {
//n is a hash table, r is a temporary array
var n = {}, r = [];

for (var i = 0; i < this.length; i++) {

If there is no current item in the hash table

if (!n[this[i]]) {

N[this[i]] = true;

Push the current item of the current array into the temporary array
R.push (This[i]);
}
}
return R;
}

3 Concise Advanced Edition

Array.prototype.unique = function () {
Return This.filter ((v, i) = = This.indexof (v) = = = = i)
}

JS Array Intermediate + Advanced tips