javascript check if it is a number 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: javascript check if string is number

// native returns true if the variable does NOT contain a valid number
isNaN(num)

// can be wrapped for making simple and readable
function isNumeric(num){
  return !isNaN(num)
}

isNumeric(123)         // true
isNumeric('123')       // true
isNumeric('1e10000')   // true (This translates to Infinity, which is a number)
isNumeric('foo')       // false
isNumeric('10px')      // false

Example 4: js check if string is number

isNaN(num)         // returns true if the variable does NOT contain a valid number

isNaN(123)         // false
isNaN('123')       // false
isNaN('1e10000')   // false (This translates to Infinity, which is a number)
isNaN('foo')       // true
isNaN('10px')      // true

Example 5: javascript check if variable is number

function isNumber(n) {
  return !isNaN(parseFloat(n)) && !isNaN(n - 0);
}

Example 6: 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