10_scope-chain.md

What is the scope chain?

• The scope chain is how Javascript resolve a variable.
• There are two scopes - Global Scope and Function Scope.
• In function scope, JavaScript looks for a variable its own scope first. If it can't find it, JavaScript looks next outer scope. If it can't find again, JavaScript keep on looking next outer, outer until it reaches the global scope.

Example 1

function foo(){
	console.log(myvar); // Error: myvar is not defined.
	                    // JavaScript can't find myvar inside foo function scope.
}

function goo(){
	var myvar = 1;
	foo();
}
goo();

Fixed Example 1

function goo(){
    var myvar = 1;
    function foo(){
        console.log(myvar); // 1
                            // JavaScript can find myvar variable its same scope.
    }	
    foo();
}
goo();