When I decided to take JavaScript seriously a while back, I realized that not fully understanding how the language handles variable scope can lead to some forehead-slapping debugging sessions. In JavaScript, a variable declaration (e.g., var foo = 1) at the end of a function will execute when the function is called, and before any code within th…

JavaScriptVariableHoisting.js

var foo = 1, 
    test;

function barOne() {
  if (!foo) var foo = 100;
  return foo;
}

test = barOne();
console.log(test); // 100

function barTwo() {
  (function () {
    var foo = 1000;
  }());
  return foo;
}

test = barTwo();
console.log(test); // 1

function barThree() {
  (function () {
    foo = 10000;
  }());
  return foo;
}

test = barThree();
console.log(test); // 10000