1.
var a // global variable
funtion aaa(){
var a // local variable
}
2.
var a // global variable
funtion aaa(){
var a //local variable
a // global variable because there is no var
3.
var a // global variable
funtion aaa(){
var a //local variable
alert(a) //it returns local because it calls the nearest one
4.
var a // global variable
funtion aaa(){
alert(a) //it returns global
5.
var a // global variable
funtion aaa(){
a // global
6.
var a // global variable
funtion aaa(){
var a //local
a // local because it affected by local var a
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<script src="greeting.js"></script> //when the web browser encounters a tag called script, it checks if there is "greeting.js" attribute(src) or no
//and then if there is any value in the attribute, reading the corresponding file
//and then it has the same effect as putting it inside here<script></script>
<title>Document</title>
</head>
<body>
<script>
function get_name(){
return ['aaa123','bbb456','ccc789'];
}
members=get_name()
for(var i=0;i<members.length;i++){
document.write(members[i].toUpperCase()+"br />");
}
var grades={'aaa123':10,'bbb456':20,'ccc789':30}; //this is an object which is always nested with {}
for(key in grades){
document.write("<li>key"+key+"value"+grades[key]+"</li>")
}
var grades={
'list' : {'aaa123':1 0,'bbb456':20,'ccc789':30}, //within the object grades, there is 'list'key and key contains value which is an another object
'show' : function(){
alert('hello world');
alert(this); //this is a variable which is point to object which function belongs, in other words, this is grades
}
}
alert(grades['show']());
var vscope = 'global';//global variable which accessible throughout the javascript
function fscope(){
var vscope = 'local'; //local variable which can be accessed only inside {}
//alert(vscope); //vscope returns 'local' because it recalled the nearest one
//if there is no vscope variable, then this will be returned 'global'
vscope = 'local'; //this is global variable because there is no var if there is no var vscope
//if there is var vscope, then this is a local variable because it affected by local var vscope
var lv = 'local variable'; //local variable
}
alert(lv); //cannot be executed because lv is local variable
function fscope2(){
alert(vscope);
}
</script>
</body>
</html>
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