use typeof code example

Example 1: get type of var js

function doSomething(x) {
  if(typeof(x) === 'string') {
    alert('x is a string')
  } else if(typeof(x) === 'number') {
    alert('x is a number')
  }
}

Example 2: check data type in javascript

typeof("string"); //string
typeof(123); //number