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How to use Functions in JavaScripts

Functions in JavaScripts

A function is a set of code that can optionally accept parameters and return a value. A JavaScript function may take zero or more parameters.

A function has three major parts:

The name of the function
Parentheses include Arguments, but Arguments are optional, An An argument is simply a value (or a reference to a value) that the function is expecting. A function might expect zero, one, two, three, or more arguments.
Body of the function between curly brackets (opening and closing)

Every function is stated with function keyword. The syntax of JavaScript function is as follows:

function function_name (optional arg1, arg2) {
block of code
}

The parameters of function are optional. you can use function without paramters. For example:

function topwebsite() {
document.write("http://www.programmersbank.com");
}

topwebsite();

Output:

http://www.programmersbank.com

Another example of JavaScript with argument is:

function topwebsite(website) {
document.write(website);
}

In this examples you have used one argument $website.

topwebsite("http://www.programmersbank.com");

Note: A function is a block of code that is not immediately executed but can be called by your scripts when needed.

function valueExpressions(value1,value2,symbol) {
symbol;
document.write(value1."+".value2);
}