Create - add - delete - change - check

1. Create an array

 

2, by

1）push , unshift

2）splice

var ARR3 = [1,2,3,4,6 ];
 var Result = arr3.splice (2,0, "SDF") // second position, delete the element 0 value inserted 
console.log (arr3)   // [. 1, 2, "SDF",. 3,. 4,. 6]

3）length

was arr = [1,2 ];
arr[arr.length] = 3
console.log(arr);   //  [1, 2, 3]

3, deleted

1) Delete a: pop, shift

2）splice

was arr2 = [1,2,3,4,6 ];
were result = arr2.splice (1.3 )
the console.log (Result)   // [2,. 3,. 4] deleted values 
the console.log (arr2 is)   // [. 1,. 6] a value obtained after the deleting
----------------------------------
var arr3 =  [1,2,3,4,6];
var result = arr3.splice(1,3,"sdf")
the console.log (Result)   // [2,. 3,. 4] deleted values 
the console.log (ARR3)   // [. 1, "SDF",. 6] delete the inserted value

3）delete

var arr = [1, 2, 3, 4];
delete arr[0];
the console.log (ARR);    // [undefined, 2,. 3,. 4] 
Delete Delete unchanged after the length of the array, only the elements removed is set to the undefined

4) array property length

There are t = [1,23,5,6,7 ];
t.length =3;
console.log(t)   // [1,23,5]

5) Empty Array

a、arr.length = 0

b、arr = [ ]

Difference:
 var ARR = [1,23,5,6,7 ];
 var of arr1 = ARR;
arr.length = 0;
console.log(arr)  // []
console.log(arr1) // []
-----------------------------            
was Arr 2 = [1,23,5,6,7 ]; 
was arr3 = Arr 2;
arr2 = [];
console.log(arr2)  // []
console.log(arr3) // [1, 23, 5, 6, 7]