How to check if a number is negative?

user_380562 0
Viewed 218353

I want to check if a number is negative. I’m searching for the easiest way, so a predefined JavaScript function would be the best, but I didn’t find anything yet. Here is what I have so far, but I don’t think that this is a good way:

function negative(number) {
  if (number.match(/^-\d+$/)) {
    return true;
  } else {
    return false;
  }
}
negative-number javascript
7 Answers

If you really want to dive into it and even need to distinguish between -0 and 0, here's a way to do it.

function negative(number) {
  return !Object.is(Math.abs(number), +number);
}

console.log(negative(-1));  // true
console.log(negative(1));   // false
console.log(negative(0));   // false
console.log(negative(-0));  // true
user_102892650

An nice way that also checks for positive and negative also...

function ispositive(n){
    return 1/(n*0)===1/0
}

console.log( ispositive(10) )  //true
console.log( ispositive(-10) )  //false
console.log( ispositive(0) )  //true
console.log( ispositive(-0) )  //false

essentially compares Infinity with -Infinity because 0===-0// true

user_48801480
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