JavaScript FunctionsJavaScript functions are used to perform operations. We can call JavaScript function many times to reuse the code. Advantage of JavaScript functionFunctions are useful in organizing the different parts of a script into the several tasks that must be completed. There are mainly two advantages of JavaScript functions.
Rules for naming functions:
How to declare a Function:To declare a function we have to use the reserved keyword "function", followed by its name, and a set of arguments. JavaScript Function SyntaxThe syntax of declaring function is given below. In the above syntax, function is a reserved keyword and "functionName" is a name given to the function. JavaScript Functions can have 0 or more arguments. JavaScript Function ExampleLet's see the simple example of function in JavaScript that does not has arguments. Test it NowOutput of the above exampleExplanation: In the above given example, we have created a function "msg" which is called by using the "onclick" event. When a user will click on this button then this function will be called and an alert box will be displayed. We can reuse the msg function as many as need in our program, so it will save memory. JavaScript Function ArgumentsWe can call function by passing arguments. Let's see the example of function that has one argument. Test it NowOutput of the above exampleExplanation: In the above example, we created a function, "getcube" having single parameter this function will be called by using "onclick" event by passing a value programmatically. When a user will click on button then this function will be called and an alert box will be displayed with calculating the cube of a given number which is 4 in above example. Function with Return ValueWe can call function that returns a value and use it in our program. Let's see the example of function that returns value. Test it NowOutput of the above exampleExplanation: In the above example, we created a function, "getinfo" which will be called automatically when document loaded. Function will return a string "Hello Javatpoint! How are you?" and "document.write" function will help to write the returned string on the document. JavaScript Function ObjectIn JavaScript, the purpose of Function constructor is to create a new Function object. It executes the code globally. However, if we call the constructor directly, a function is created dynamically but in an unsecured way. SyntaxParameterarg1, arg2, .... , argn - It represents the argument used by function. functionBody - It represents the function definition. JavaScript Function MethodsLet's see function methods with description.
JavaScript Function Object ExamplesExample 1Let's see an example to display the sum of given numbers. Test it NowOutput: 7 Example 2Let's see an example to display the power of provided value. Test it NowOutput: 8 Next TopicJavascript Objects |