check if number in string javascript 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: javascript is variable a string

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

Example 3: check if a string contains digits js

function hasNumber(myString) {
  return /\d/.test(myString);
}

Example 4: javascript check if string is number

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