JavaScript_Succinctly

Sample: sample112.html
var foo = function () {
var boo = function () {
bar = 2; // No var used, so bar is placed in the global scope at
window.bar
} ();
} ();
console.log(bar); // Logs 2, because bar is in the global scope.
// As opposed to...
var foo = function () {
var boo = function () {
var doo = 2;
} ();
} ();
// console.log(doo); logs undefined. doo is in the boo function scope, so
an error occurs
The concept to take away here is that you should always use var when defining
variables inside of a function. This will prevent you from dealing with potentially
confusing scope problems. The exception to this convention, of course, is when you
want to create or change properties in the global scope from within a function.
The scope chain (aka lexical scoping)
There is a lookup chain that is followed when JavaScript looks for the value associated
with a variable. This chain is based on the hierarchy of scope. In the code that follows, I
am logging the value of sayHiText from the func2 function scope.
Sample: sample113.html
var sayHiText = 'howdy';
var func1 = function () {
var func2 = function () {
console.log(sayHiText); // func2 scope, but it finds sayHiText in
global scope.
} ();
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