Function Definition. 6. Functions are defined, or declared, with the function keyword. Defining a Function. When an object is created using the constructor, it inherits all its properties and methods: Example Copy This section explains how to write your own functions in JavaScript. Create a constructor function Accumulator(startingValue).. Let’s see an example: Read on for a full explanation. In this tutorial, we will learn several ways to define a function, call a function, and use function parameters in JavaScript. When an inherited function is executed, the value of this points to the inheriting object. JavaScript allows us to write our own functions as well. A factory function is any function which is not a class or constructor that returns a (presumably new) object. (x, y) are parameters, variable names for the inputs a function will accept. Object that it creates should: Store the “current value” in the property value.The starting value is set to the argument of the constructor startingValue. Code language: JavaScript (javascript) When a function creates an object, it is called a factory function. In JavaScript functions are first-class objects - a function is a regular object of type function. In your first statement the constructor function called is an already defined function, Function . There’s a lot going on in the example above, so let’s look at each part individually. Note, that when a function is called with the new keyword in javascript it exhibits special behavior. One more thing: new Function. The ways of the declaration described above create the same function object type. Below is the syntax for a function in JavaScript. You can add functions to this prototype property, and in this form, it is known as a method. Every JavaScript function has a prototype property, which is empty by default. Normally, it is better to use new Function() than eval() to evaluate code: The function parameters provide a clear interface to the evaluated code and you don’t need the slightly awkward syntax of indirect eval() in order to ensure that the evaluated code can only access its own and global variables. JavaScript functions are a special type of objects, called function objects. function nameOfFunction() { // Code to be executed } It works like creating a new function, but as functions are objects in JavaScript, you create an object. ; addTwoNumbers is the function’s name, which is customizable — just like variable names. In JavaScript, any function can return an object. function is the keyword that starts declaring a function. The createPerson() is a factory function because it returns a new person object. (It is possible to attach a new function to a instance in JavaScript). Before we use a function, we need to define it. The code is literally just a string. 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