I am new to JavaScript and I was doing some practices on local and global variable scopes. Following is my code(fiddle):
var myname = "initial" function c(){ alert(myname); var myname = "changed"; alert(myname); } c();
When the first alert is called, it is showing myname
as undefined. So my confusion is why I am not able to access a global instance of myname
and if I don't define myname
within the function then it will work fine.
In JavaScript, the variable declarations are automatically moved to the top of the function. So, the interpreter would make it look more like this:
var myname = "initial" function c(){ var myname; // Alerts undefined alert(myname); myname = "changed"; // Alerts changed alert(myname); } c();
This is called hoisting.
Due to hoisting and the fact that the scope for any variable is the function it's declared in, it's standard practice to list all variables at the top of a function to avoid this confusion.
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