1 var sth = ""; // Global Scope
2 var foo = function(){
var sth = ""; // Local Scope
}
3 var foo = function(){
sth = ""; // Global Scope, this is definitely denied!
}
4 (function(){
var jQuery = {
// variable methods or definitions
}
window.jQuery = jQuery;
})(); // Immediately-Invoked Function Expressions, This is used by jQuery and some other liberaries.
point1: the var exsits in var jQuery is very important, without it jQuery will be global scope.
point2: though the jQuery is also global scope, but when another jQuery defined in window, it will also work.
according to http://learn.jquery.com/javascript-101/scope/
5 closure
for(var i=0;i<5;i++){
setTimeOut(function(){
alert(i); // will not alert correctly~， because the i has already added for 5 times in the fiven 1000 mill-seconds.
}, 1000);
}
to correct this, we should use closure.
for (var i=0;i<5;i++) {
setTimeOut(alertFunc(i), i*1000); // why? the function will be called immediately with parameter i, so the alertFunc knows that i, and only i nothing else, then alert 0, 1, 2, 3, 4, end~
}
var alertFunc = function(i){
alert(i);
}
according to http://learn.jquery.com/javascript-101/closures/