Function in Javascript
Table of Content:
JavaScript Functions
JavaScript functions are used to perform operations. We can call JavaScript function many times to reuse the code.
A function is a set of statements that performs a tasks or calculates a value. Functions may also take inputs, process them and return the output.
Advantage of JavaScript function
There are mainly two advantages of JavaScript functions.
- Code reusability: We can call a function several times so it save coding.
- Less coding: It makes our program compact. We don’t need to write many lines of code each time to perform a common task.
JavaScript Function Syntax
The syntax of declaring function is given below.
function functionName([arg1, arg2, ...argN]){ //code to be executed }
JavaScript Functions can have 0 or more arguments.
JavaScript Function Example
Let’s see the simple example of function in JavaScript that does not has arguments.
Like most programming languages, function is a piece of code that can be isolated to be called multiple times. Example of a function:
function Hello(string) { return "Hello" + " " + string; } Hello( "Tom"); /* returns "Hello Tom" */
Function as value
Functions are values in JavaScript. A function can be assigned as a value to a variable.
var f = function foo() { console.log("Hello"); }; f(); /* returns "Hello" */
Function as argument
A function can be passed as an argument to another function.
var f = function() { console.log("Hello"); }; var executor = function(fn) { fn(); } executor(f); /* returns "Hello" */ ```
Function as property
Functions can be added as a property to an object.
var myObj = { "testProp" : true }; myObj.prop1 = function() { console.log ("Function in object"); }; myObj.prop1();
Function arguments
A function can accept a varied number of arguments. i.e., a function "add" can be called by passing a different number of arguments different times. This is possible using an implicit argument by JavaScript called arguments
.
var add = function() { var i, sum = 0; for (i=0; i< arguments.length; i++) { sum += arguments[i]; } return sum; }; console.log(add(1,2,3,4,5)); /* 5 arguments*/ console.log(add(1,2,3,4)); /* 4 arguments*/