javascript check if variable is a number code example

Example 1: 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 2: javascript check if a value is an int

// The Number.isInteger() checks to see if the passed value is an integer
// Returns true or false

Number.isInteger(2); //True
Number.isInteger(90); //True
Number.isInteger("37"); //False
Number.isInteger(false); //false

Example 3: javascript check if a value is a integer number

Number.isInteger(123) //true
Number.isInteger(-123) //true
Number.isInteger(5-2) //true
Number.isInteger(0) //true
Number.isInteger(0.5) //false
Number.isInteger('123') //false
Number.isInteger(false) //false
Number.isInteger(Infinity) //false
Number.isInteger(-Infinity) //false
Number.isInteger(0 / 0) //false

Example 4: check if something is a number

<html>
<head></head>
<body>
<h1>isNaN() example</h1>

<script type="text/javascript">
 var num1 = 100;
 if(isNaN(num1)){
    document.write(num1 + " is not a number <br/>");
 }else{
    document.write(num1 + " is a number <br/>");
 }
 
 var str1 = "mkyong"
 if(isNaN(str1)){
    document.write(str1 + " is not a number <br/>");
 }else{
    document.write(str1 + " is a number <br/>");
 }
</script>

</body>
</html>

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