JavaScript Variables

javascript-vars.js

dontDoThis = 'ever !!!';

var a;
if (a === undefined){
  console.log('a is ' + a); // 'a is undefined'
}
if (b) {} // this will generate an error "ReferenceError: b is not defined"

var n = null;
console.log(n * 32); // 0. Note: implicit type conversion

var c = 1, d, e = {};
console.log(c, d, e); // 1 undefined {}