JavaScript Functions

A function is a set of statements that take inputs, do some specific computation, and produce output. The idea is to put some commonly or repeatedly done tasks together and make a function so that instead of writing the same code again and again for different inputs, we can call that function.

Function Definition: Before, using a user-defined function in JavaScript we have to create one. We can use the above syntax to create a function in JavaScript. A function definition is sometimes also termed a function declaration or function statement. Below are the rules for creating a function in JavaScript:

• Every function should begin with the keyword function followed by,

• A user-defined function name that should be unique,

• A list of parameters enclosed within parentheses and separated by commas,

• A list of statements composing the body of the function enclosed within curly braces {}.

Function Declaration: It declares a function with a function keyword. The function declaration must have a function name.

Function Expression: It is similar to a function declaration without the function name. Function expressions can be stored in a variable assignment.

Function Parameters: Till now we have heard a lot about function parameters but haven’t discussed them in detail. Parameters are additional information passed to a function.

Calling Functions: After defining a function, the next step is to call them to make use of the function. We can call a function by using the function name separated by the value of parameters enclosed between the parenthesis and a semicolon at the end.

Return Statement: There are some situations when we want to return some values from a function after performing some operations. In such cases, we can make use of the return statement in JavaScript. This is an optional statement and most of the time the last statement in a JavaScript function.