JSFiddle - React, Tailwind, and code Playground

by Chuan Shao

JavaScript

//Evaluate to undefined

var a;
console.log(a);

function Sample(x){
  this.x = x;
}
var s = new Sample();
console.log(s.x)
console.log(s.notExistVariable);

var n = [2,3,4];
console.log(n[8]);

function test(){
  //no return value for this function
}
console.log(test());

function test2(){
  return;
}
console.log(test2());

console.log(null == undefined);
console.log(null === undefined);