how to check data type of value in javascript 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: how to get type of variable in javascript

> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"