JavaScript variable scopes

There are only two scenarios for JavaScript variable scopes: global scope, function scope

There is no code block scope, so develop a programming habit of declaring all variables (file headers, function headers).

function test () {     
    var abc= "123";     
    Efg= "456";     
    Put ("in Test abc=" +ABC);     
    Put ("in Test efg=" +EFG);     
}     
        
function Test1 () {     
    var abc;     
    Put ("in Test1 abc=" +ABC);     
}     

var abc= "abc";
var efg= "EFG";

Test1 ();
Put ("Before Test abc=" +ABC);
Put ("Before Test efg=" +EFG);
Test ();
Test1 ();
Put ("After test abc=" +ABC);
Put ("After test efg=" +EFG);

{     
    var abc= "www";
    Put ("in Block abc=" +ABC);
}
    Put ("Out Block abc=" +ABC);

Debugging information:

In Test1 abc=undefined

Before Test ABC=ABC

Before Test EFG=EFG

In Test abc=123

In Test efg=456

In Test1 abc=undefined

After Test ABC=ABC

After Test efg=456

In Block abc=www

Out Block Abc=www

This article is from the "idata" blog, please be sure to keep this source http://idata.blog.51cto.com/4581576/1100248