Javascript check >= 0 not null or undefined or ''

Question

What is the most convenient / performant way to check if a variable is greater than or equal to 0 and not null or undefined or '' ? eg [0, Infinity) . Let's say my variable is x , the obvious x >= 0 doesn't work as null >= 0 is true . The best I could come up with was.

x > 0 || x === 0

Can anyone think of a better one?

It seems like this question should already exist so if someone can find this question I'm happy to delete mine.

Answer 1

Perhaps not the answer you're looking for but why not check for number first?

if (typeof x === "number" && x >= 0) {
  // Excludes non-number values such as null and undefined
}

Note that this will allow Infinity , if you want finite numbers only:

if (typeof x === "number" && isFinite(x) && x >= 0) {
  // ...
}

The number type check clarifies your intent .

Any attempt to make it short and smart will most likely rely on type coercion which is risky, complicated (not everybody is familiar with JS quirks) and unnecessary from a performance point of view.

Answer 2

Try this:

if (x != null && x >= 0)
{
    //then insert the code to be executed here
}

Answer 3

The not null call could be as follows

value !== null

And i think you should just keep the above zero check your already doing!

Answer 4

You could check for zero directly and omit falsy values for the second check.

x === 0 || !x && x > 0
-------                    only zero
           --              no other falsy values
                 -----     a non falsy value which is greater then zero

Answer 5

You can just check if the variable has a truthy value or not. That means

if( value ) { } will evaluate to true if value is not:

null undefined NaN empty string ("") 0 false The above list represents all possible falsy values in ECMA-/Javascript. Find it in the specification at the ToBoolean section.

Further read: http://typeofnan.blogspot.com/2011/01/typeof-is-fast.html

Answer 6

Use non-strict comparison with null and then compare numbers:

 function check(x) { return x != null && 0 <= x; } console.log(check(1), true); console.log(check(0), true); console.log(check(-1), false); console.log(check(null), false); console.log(check(undefined), false); console.log(check('1'), true); console.log(check('0'), true); console.log(check('Hello'), false); console.log(check('-1 and 2 and 3'), false);