How to Call a Function in JavaScript

Functions--named groups of statements that can be "called" or "invoked"--lie at the heart of JavaScript. Functions can be given special inputs, called "parameters" or "arguments", which control what they do. Once defined, a function can be called over and over again with different parameters. In JavaScript, functions are called by writing the name of the function followed by a pair of parentheses containing the parameters, if any.

Things You'll Need

• JavaScript or text editor

Instructions

Call a Function in JavaScript

1. Define the function to be called, using the following syntax. Or, identify an existing function that you want to call.
   function NAME (parameter 1, parameter 2, ...) { statement(s) }

2. Call the function by writing its name, a left parenthesis, parameters if any separated by commas, and a right parenthesis. For instance, to call the built-in alert function, simply code the following:
   alert("This is a call to the alert function.");

3. Call a function assigned to a variable by coding the variable's name, also followed by a parenthesized parameter list. Consider the following example:
   var back_or_forward = go_back ? history.back : history.forward;
back_or_forward ();

4. Capture the return value from the function, if any, by placing the function call on the right side of an assignment statement, or anywhere else an expression is required. Examples:
   user_input = prompt("Your name");