js string is number code example

Example 1: 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 2: js is number

Number.isInteger(value)

Example 3: 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 4: javascript check if string is number

function isNumeric(num){
  return !isNaN(num)
}
isNumeric("23.33"); //true, checking if string is a number.

Example 5: js check if string is integer

function isInt(str) {
  return !isNaN(str) && Number.isInteger(parseFloat(str));
}