Reverse retrieval in javascript and reverse retrieval ~~ Meaningless _ javascript tips-js tutorial

Operator ~, It means bitwise inversion. On the surface ~~ It doesn't make sense. Here is a good example. You can refer to the following operators ~, It means bitwise inversion. On the surface ~~ It doesn't make sense. In fact, you can convert a floating point number into an integer in JS.

The Code is as follows:

Script
Var myArray = new Array ();
MyArray. push ("");
MyArray. push ("B ");
MyArray. push ("c ");
MyArray. push ("d ");

// Now we need to randomly retrieve an element from the array.
Var random = myArray [~~ (Math. random () * myArray. length)]; // Math. random () returns a pseudo-random number between 0 and 1, which may be 0, but always less than 1)

Var I = 7.94;
I = ~~ I;
Alert (I );

Var j = 7.34;
J = ~~ J;
Alert (j );

Script

As shown above, if no ~~, The random result is a decimal number, which is to remove the decimal number and retain the integer. For example, I = 7, j = 7. However, this mechanism does not exist in C. In C, float cannot be reversed by bit, and forced type conversion can be used in C (whereas in JS, this mechanism is not available, floating Point to integer) to achieve the same purpose (discard the fractional part, retain the integer part ).