Check if two numbers are both positive or both negative

Question

I did not find a better name for this question...

I want to check if two numbers are either both smaller than 0, both 0 or both greater than 0. Is there an easier way than this?

if (nr0 < 0 && nr1 < 0 || nr0 == 0 && nr1 == 0 || nr0 > 0 && nr1 > 0) {
    //do smth...
}

Ollin Boer Bohan · Answer 1 · 2018-08-10T16:11:05.973

14

For readability and simplicity I would suggest:

if (Math.sign(nr0) == Math.sign(nr1)) {
    //...
}

From MDN:

If the argument is a positive number, negative number, positive zero or negative zero, [Math.sign] will return 1, -1, 0 or -0 respectively. Otherwise, NaN is returned.

edited Aug 10 '18 at 16:11

answered Aug 10 '18 at 15:55

Ollin Boer Bohan

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score 3 · Accepted Answer · answered Aug 10 '18 at 15:55

3

You can multiply the numbers and check the multiplication should be positive (this will cover both being negative and both being positive) or they should be equal (which will cover the 0 case)

if(nr1*nr2 > 0 || (nr1 === nr2)){
    console.log("On the same side of number scale");
}

answered Aug 10 '18 at 15:55

void

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Depending on numbers this can cause integer overflow, so I wouldn't rely on that solution too much. – Ivan Yurchenko Jul 22 '20 at 20:58
This does not work for very small numbers, e.g. `-1e-64 * -1e-1164 > 0` is `false`. – user1346466 Apr 19 '22 at 10:23

Bibek Shah · Answer 3 · 2018-08-10T16:05:27.983

1

One way would be:

if ( nr0 * nr1 > 0 || (nr0 == 0 && nr1 == 0)) {
    // do sth...
}

edited Aug 10 '18 at 16:05

answered Aug 10 '18 at 15:56

Bibek Shah

419
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19

Check if two numbers are both positive or both negative

3 Answers3