A powerful function of an array splice,[, delete, change]

 1 //  var a = [n/a]; 
2 //  a.splice (0); 3 //  Console.log (a); >>[]
4 //  A.splice (1); 5 //  Console.log (a); >>[1]
 6 //  A.splice (0,1); 7 //  Console.log (a); >>[2,3] 

The first parameter represents starting from the beginning, the second parameter means deleting a few, if not written, or just writing a parameter 0, will delete all.

1//var a = [[+]
2//  A.splice (0,0,6); 3 // Console.log (a); >>[6, 1, 2, 3]

The third parameter indicates that a value is added, which is represented in this line of code, starting with the No. 0, deleting 0 values and adding a 6 from the No. 0 index.

1 // var a = [[+] 2 // A.splice (0,1,6); 3 // Console.log (a); >>[6, 2, 3] 4 // A.splice (1,1,6); 5 // Console.log (a); >>[1, 6, 3]

If the second argument is not written in 0, then the third argument can be used as a replacement, which is, of course, a small trick.

1 // A.splice (1,0,1.1,1.2,1.3); 2 // Console.log (a); >>[1, 1.1, 1.2, 1.3, 2, 3]

You can add an arbitrary value after the second argument

A powerful function of an array splice,[, delete, change]