js how to test if something 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 number

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

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

Example 3: javascript check if variable is number

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