check if value is number js code example

Example 1: javascript check if number

//Updated dec 2020
// The first 2 Variations return a Boolean
// They just work the opposite way around

// IsInteger
if (Number.isInteger(val)) {
	// It is indeed a number
}

// isNaN (is not a number)
if (isNaN(val)) {
	// It is not a number
}

// Another option is typeof which return a string
if (typeof(val) === 'number') {
	// Guess what, it's a bloody number!
}

Example 2: javascript check if number

// The first 2 Variations return a Boolean
// They just work the opposite way around

// IsInteger
if (Number.isInteger(val)) {
	// It is indeed a number
}

// isNaN (is not a number)
if (isNaN(val)) {
	// It is not a number
}

// Another option is typeof which return a string
if (typeof(val) === 'number') {
	// Guess what, it's a bloody number!
}

Example 3: integer check in javascript

var a=Number.isInteger(5); //True
var b= Number.isInteger(01); //True
var c=Number.isInteger("10"); //False

console.log(a,b,c);  //true true false

Example 4: check if input is a number javascript

// Another option is typeof which return a string
if (typeof(val) === 'number') {
	// Guess what, it's a bloody number!
}

Example 5: javascript is variable a string

if (typeof myVar === 'string'){
    //I am indeed a string
}

Example 6: javascript check if number

function isNumber(n) { return /^-?[\d.]+(?:e-?\d+)?$/.test(n); } 

------------------------

isNumber('123'); // true  
isNumber('123abc'); // false  
isNumber(5); // true  
isNumber('q345'); // false
isNumber(null); // false
isNumber(undefined); // false
isNumber(false); // false
isNumber('   '); // false