JAVASCRIPT

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

js is number

Number.isInteger(value)

js is numeric

function isNumeric(num) {
    if (num === '' || num === null) {
        return false
    }
    return !isNaN(num)
}

isNumeric('') //false
isNumeric('7') //true
isNumeric(7) //true
isNumeric('7a') //false
isNumeric('a') //false
isNumeric(null) //false
isNumeric(0) //true
isNumeric('0') //true
isNumeric(true) //true
isNumeric(false) //true

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

javascript js isNumber

// strict, matches only objects of type 'number'
// excluding Infinity and NaN.
function isNumber(n) {
    return typeof n === 'number' && isFinite(n);
}