JS Array Common methods, the copy of the array (does not affect the original array), the array of equal __JS

Ways to change the original array:POPs (); Deletes the first element of the tail and returns the element;

var a = [1,2,3];
var B = A.pop ();
Console.log (a);//[1,2]
Console.log (b);//3

Similar methods:
push (); tail pushing; returning array length;
Shift (); top eject; return the element;
Unshift (), top sub-entry, return array length, reverse (), reverse array, return inverted array, splice (); Common method; Returns the array of deleted numbers, which can be []; methods that do not change the original array:Concat: Returns the concatenation of the array, does not change the original array; forEach; Map; join (); Returns the concatenation of the string, you can specify the interval;

Attention:
[1,2,3].join (')
//"123"
[1,2,3].join ()
//"1,2,3"

Slice (start,end); intercept the array, return the intercepted part, do not change the original array; sort (); Pass a function as an argument, which can be controlled in ascending order, descending or random; (try to produce random numbers); toString (); [1,2,3].tostring () ==[1,2,3].join (); Array Copy

An array is a reference type; simple assignment simply adds a pointer to an array; ex:

var a = [1,2,3];
var b = A;
B.push (2);
Console.log (a)//[1,2,3,2]

So how to achieve a separate copy. Introduce the following two methods: The performance of the two methods is not significant, different browser kernels have advantages and differences:

Method 1
var a = [1,2,3];
var B = A.slice ();
A.reverse;
Console.log (a);//[3,2,1]
Console.log (b);//[1,2,3]
//Method 2
var c = [4,5,6];
var d = c.concat ();
C.reverse ();
Console.log (c);//[6,5,4]
Console.log (d);//[4,5,6]

Array Equality

Let's talk about the pit first:
Any two array equality returns FALSE;[]=[];//FALSE
What to do. Do not compare each item to see the method available above: toString ();
The conversion to a string is more than once.