js check if string is number

1//Updated dec 2020
2// The first 2 Variations return a Boolean
3// They just work the opposite way around
4
5// IsInteger
6if (Number.isInteger(val)) {
7	// It is indeed a number
8}
9
10// isNaN (is not a number)
11if (isNaN(val)) {
12	// It is not a number
13}
14
15// Another option is typeof which return a string
16if (typeof(val) === 'number') {
17	// Guess what, it's a bloody number!
18}

1// native returns true if the variable does NOT contain a valid number
2isNaN(num)
3
4// can be wrapped for making simple and readable
5function isNumeric(num){
6  return !isNaN(num)
7}
8
9isNumeric(123)         // true
10isNumeric('123')       // true
11isNumeric('1e10000')   // true (This translates to Infinity, which is a number)
12isNumeric('foo')       // false
13isNumeric('10px')      // false

1// The first 2 Variations return a Boolean
2// They just work the opposite way around
3
4// IsInteger
5if (Number.isInteger(val)) {
6	// It is indeed a number
7}
8
9// isNaN (is not a number)
10if (isNaN(val)) {
11	// It is not a number
12}
13
14// Another option is typeof which return a string
15if (typeof(val) === 'number') {
16	// Guess what, it's a bloody number!
17}

1if (typeof myVar === 'string'){
2    //I am indeed a string
3}

1isNaN(num)         // returns true if the variable does NOT contain a valid number
2
3isNaN(123)         // false
4isNaN('123')       // false
5isNaN('1e10000')   // false (This translates to Infinity, which is a number)
6isNaN('foo')       // true
7isNaN('10px')      // true

1function isNumber(n) { return /^-?[\d.]+(?:e-?\d+)?$/.test(n); } 
2
3------------------------
4
5isNumber('123'); // true  
6isNumber('123abc'); // false  
7isNumber(5); // true  
8isNumber('q345'); // false
9isNumber(null); // false
10isNumber(undefined); // false
11isNumber(false); // false
12isNumber('   '); // false