How to check if a variable is an integer in JavaScript?
Number.isInteger()
seems to be the way to go.
MDN has also provided the following polyfill for browsers not supporting Number.isInteger()
, mainly all versions of IE.
Link to MDN page
Number.isInteger = Number.isInteger || function(value) {
return typeof value === "number" &&
isFinite(value) &&
Math.floor(value) === value;
};
That depends, do you also want to cast strings as potential integers as well?
This will do:
function isInt(value) {
return !isNaN(value) &&
parseInt(Number(value)) == value &&
!isNaN(parseInt(value, 10));
}
With Bitwise operations
Simple parse and check
function isInt(value) {
var x = parseFloat(value);
return !isNaN(value) && (x | 0) === x;
}
Short-circuiting, and saving a parse operation:
function isInt(value) {
if (isNaN(value)) {
return false;
}
var x = parseFloat(value);
return (x | 0) === x;
}
Or perhaps both in one shot:
function isInt(value) {
return !isNaN(value) && (function(x) { return (x | 0) === x; })(parseFloat(value))
}
Tests:
isInt(42) // true
isInt("42") // true
isInt(4e2) // true
isInt("4e2") // true
isInt(" 1 ") // true
isInt("") // false
isInt(" ") // false
isInt(42.1) // false
isInt("1a") // false
isInt("4e2a") // false
isInt(null) // false
isInt(undefined) // false
isInt(NaN) // false
Here's the fiddle: http://jsfiddle.net/opfyrqwp/28/
Performance
Testing reveals that the short-circuiting solution has the best performance (ops/sec).
// Short-circuiting, and saving a parse operation
function isInt(value) {
var x;
if (isNaN(value)) {
return false;
}
x = parseFloat(value);
return (x | 0) === x;
}
Here is a benchmark: http://jsben.ch/#/htLVw
If you fancy a shorter, obtuse form of short circuiting:
function isInt(value) {
var x;
return isNaN(value) ? !1 : (x = parseFloat(value), (0 | x) === x);
}
Of course, I'd suggest letting the minifier take care of that.
Use the === operator (strict equality) as below,
if (data === parseInt(data, 10))
alert("data is integer")
else
alert("data is not an integer")