Operator // in JavaScript : 5.0 // 2.0 = 5?

Question

Is there a // operator in JavaScript?

Because in Python we have:

5 // 2.0 # => 2.0
5 / 2.0  # => 2.5

So I tried in JavaScript:

5.0//2.0 

and I got 5 ? What's going on there?

I read that there is no such a thing as a // operator in JavaScript. In this case, why didn't I get an exception or, better, an error from the lexer?

I used this line:

document.write(eval("5.0//2.0"));

In Firefox 3.6.23.

Answer 1

// is a comment in javascript.

Try:

   5 / 2; //yields 2.5
   Math.floor(5/2); //yields 2

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Also do not use eval.

Just do document.write(5/2);

Answer 2

在JavaScript中， //不是运算符，它表示注释。

Answer 3

//用于在JavaScript中进行评论。

Answer 4

// starts a comment. To do integer division, first perform a regular division using / and then round it. This can be done with &-1 , ^0 , |0 or ~~ , in order from fast to slow as measured on my laptop. There is a measurable difference between the first three but it's small. The last one is really slow in comparison.

Putting it all together, 5/2&-1 will yield 2. It rounds towards zero.

Answer 5

You want to use ~~ 5/2 to get 2. NO need to download math. library