Edit in JSFiddle

//handy for string, number, and boolean primtive values
console.log(typeof ""); //logs string
console.log(typeof 4); //logs number
console.log(typeof true); //logs boolean
console.log(typeof undefined); //logs undefined

//But buggy when it comes to null
console.log(typeof null); //WHAT? buggy! logs Object, not 'null'