CODEWITHSUNDEEP
javascriptsyntax
Mark Fox
Mark Fox

Reputation: 8924

Function and variable with the same name

The following code-snippet is a test to see what happens when a function and a variable share the same name in the same scope. In Chrome it appears the variable definition has precedence in reference.

  1. Can the named function be executed, or is it completely obscured by the variable declaration?
  2. Is it the standard behavior in Javascript that variables take precedence over functions with the same name?

Sorry for the two part question, but it seemed wasteful to ask two separate questions.

Code:

<!DOCTYPE html>
    <head>
        <meta charset="utf-8">
        <title></title>
    </head>
    <body>
        <script>

            var overlapping = function() { return 'this is a var holding an anonymous function' };

            function overlapping()
            {
                return 'this is a function definition';
            }

            output( overlapping, 'overlapping' );
            output( overlapping(), 'overlapping()' );

            function output( expression, description )
            {
                document.writeln( '<li>' + ( description ? ('<i>' + description + '</i>: ') : '' ) + expression + '</li>' );
            }
        </script>
    </body>
</html>

Upvotes: 31

Views: 19579

Answers (2)

SridharKritha
SridharKritha

Reputation: 9611

  1. Can the named function be executed, or is it completely obscured by the variable declaration?

    Function declaration will not be executed there. Because of the same name usage the function expression overrides the function declaration.

  2. Is it the standard behavior in Javascript that variables take precedence over functions with the same name?

    Is not about preferring one over other. In JavaScript, function declarations are hoisted to the top of the enclosing function or global scope. Function expression of same variable name overrides the function declaration.

Example:

   foo(); // Function Declaration - will be hoisted
   foo = function() { console.log("Function Expression  - will NOT be hoisted"); };
   function foo()   { console.log("Function Declaration - Will be hoisted"); }
   foo(); // Function Expression  - will NOT be hoisted

Upvotes: 0

Niko
Niko

Reputation: 26730

In JavaScript, function definitions are hoisted to the top of the current scope. Your example code therefore reads as:

var overlapping = function() { return 'this is a function definition' };
var overlapping = function() { return 'this is a var holding an anonymous function' };

This is some good read about this topic: http://www.adequatelygood.com/2010/2/JavaScript-Scoping-and-Hoisting

Upvotes: 19

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