This section provides a tutorial example on how local variables behave inside and outside functions.
To see how local variables behave inside and outside functions, I wrote the following
tutorial example:
<html>
<!-- Local_Variable_Scope.html
Copyright (c) 2008 by Dr. Herong Yang, http://www.herongyang.com/
-->
<head><title>Local Variable Scope</title></head>
<body>
<pre>
<script type="text/javascript">
scopeCheck();
document.write("\n\nAfter function call:");
// localVar is not a valid variable
// document.write("\n localVar = " + localVar);
document.write("\n localVar is not valid");
// localNoVar is a valid variable, auto-declared by scopeCheck()
document.write("\n localNoVar = " + localNoVar);
function scopeCheck() {
var localVar;
localVar = "Apple";
localNoVar = "Orange";
localVar = localVar + " - Updated";
localNoVar = localNoVar + " - Updated";
document.write("\n\nUpdated value in function:");
document.write("\n localVar = " + localVar);
document.write("\n localNoVar = " + localNoVar);
}
</script>
</pre>
</body>
</html>
This tutorial example tests two "local" variables: one declared with a "var" statement, and one without.
They behave differently. "localVar" declared with a "var" statement is a true local variable.
"localNoVar" auto-declared without a "var" statement becomes a global variable.
See the output:
Updated value in function:
localVar = Apple - Updated
localNoVar = Orange - Updated
After function call:
localVar is not valid
localNoVar = Orange - Updated
