Defining a Function. 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. 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. Note, that when a function is called with the new keyword in javascript it exhibits special behavior. The createPerson() is a factory function because it returns a new person object. Create a constructor function Accumulator(startingValue).. Every JavaScript function has a prototype property, which is empty by default. function nameOfFunction() { // Code to be executed } When an inherited function is executed, the value of this points to the inheriting object. A factory function is any function which is not a class or constructor that returns a (presumably new) object. Let’s see an example: It works like creating a new function, but as functions are objects in JavaScript, you create an object. Function Definition. (It is possible to attach a new function to a instance in JavaScript). When an object is created using the constructor, it inherits all its properties and methods: Example Copy JavaScript allows us to write our own functions as well. In this tutorial, we will learn several ways to define a function, call a function, and use function parameters in JavaScript. A function object includes a string which holds the actual code -- the function body -- of the function. The following code uses the createPerson() factory function to create two objects john and jane: You can add functions to this prototype property, and in this form, it is known as a method. Read on for a full explanation. In your first statement the constructor function called is an already defined function, Function . Before we use a function, we need to define it. The code is literally just a string. A JavaScript Function is a JavaScript Variable until it is executed (evaluated). JavaScript functions are a special type of objects, called function objects. ; addTwoNumbers is the function’s name, which is customizable — just like variable names. Code language: JavaScript (javascript) When a function creates an object, it is called a factory function. If it does not find there then it uses studObj's __proto__ link which points to the prototype object of Student function. Functions are defined, or declared, with the function keyword. 6. Below is the syntax for a function in JavaScript. function is the keyword that starts declaring a function. (x, y) are parameters, variable names for the inputs a function will accept. 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