Check if a number has a decimal place/is a whole number

Question

I am looking for an easy way in JavaScript to check if a number has a decimal place in it (in order to determine if it is an integer). For instance,

23 -> OK
5 -> OK
3.5 -> not OK
34.345 -> not OK

if(number is integer) {...}

Answer 1

Using modulus will work:

num % 1 != 0
// 23 % 1 = 0
// 23.5 % 1 = 0.5

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Note that this is based on the numerical value of the number, regardless of format. It treats numerical strings containing whole numbers with a fixed decimal point the same as integers:

'10.0' % 1; // returns 0
10 % 1; // returns 0
'10.5' % 1; // returns 0.5
10.5 % 1; // returns 0.5