<script>
name = "Tim";
function greet() {
console.log(name);
var name = "David" ;
}
greet();
</script>
Why does the result show "undefined"? I expected Tim or David.
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Here is the extensive explanation [stackoverflow.com/a/9085872/2413470][1] [1]: stackoverflow.com/a/9085872/2413470spring– spring2013-06-21 07:20:13 +00:00Commented Jun 21, 2013 at 7:20
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2 Answers
The first 'name' you declare is a global variable. Inside the function, you declare it again, so you lose the visibility of the global one. But you use the variable before it is defined.
name = "Tim"; // global name here
function greet() {
// var name; // here name is automatically declared ( because of hoisting ) but undefined
console.log(name); // here you use name before it is defined
var name = "David" ; // here name is defined
}
greet();
Javascript has scope in functions, that's important. Google for 'javascript hoisting' it will help.
1 Comment
musicnothing
+1 Exactly. Javascript sees the re-declaration of the variable in the new scope, so it cancels out the original, but then it's used before it's set.
Chage it like this,
var name = "Tim";
function greet() {
console.log(name);
name = "David" ;
}
greet();
