Typescript window add property

How to Add Objects to the Window Namespace in TypeScript

Learn how to add new properties to the window object in TypeScript, create interfaces, deal with exports and Webpack, and use namespaces for logical grouping of functionalities. Find out how to extend the Window type and access the global object in different JavaScript environments. Improve your coding skills with TypeScript and the window object.

TypeScript is a superset of JavaScript that allows for the introduction of static typing to JavaScript. It enables developers to write more robust code by providing additional features such as interfaces, classes, and modules. The window object in javascript is a global object that represents the browser window. The window object provides access to various properties and methods related to the browser window. In this article, we will discuss how to explicitly add a new property to the window object in TypeScript.

Adding a New Property to the Window Object in TypeScript

TypeScript allows for adding a new property to the window object explicitly. This means that you can add new properties to the window object without the risk of overwriting existing properties. The following code demonstrates how to add a new property to the window object:

declare global  interface Window  myProp: string; > >window.myProp = "Hello World"; 

In this example, we declare a new interface called “Window” and add a new property called “myProp” to it. We then assign a value of “Hello World” to the “myProp” property of the window object. This new property is now available globally and can be accessed from anywhere in the application.

Creating an Interface by Extending the Window Object

An interface can be created by extending the Window object. This allows for the creation of a custom interface that inherits all the properties and methods of the Window object. The following code demonstrates how to create an interface by extending the Window object:

interface MyWindow extends Window  myProp: string; >const myWindow: MyWindow = window as MyWindow; myWindow.myProp = "Hello World"; 

In this example, we define a new interface called “MyWindow” that extends the Window object. We then create a new variable called “myWindow” that is of type “MyWindow”. We can then access the “myProp” property of the “myWindow” object and assign a value of “Hello World” to it.

Dealing with Exports and Webpack

Webpack is a popular module bundler that allows for the creation of modular JavaScript applications. When using Webpack, it may not make all exports available from the window namespace. In order to explicitly define exports in code, you can use the “export” keyword. The following code demonstrates how to do so:

declare global  interface Window  myFunction: () => void; > >export const myFunction = () =>  console.log("Hello World"); >;window.myFunction = myFunction; 

In this example, we declare a new interface called “Window” and add a new function called “myFunction” to it. We then define a new function called “myFunction” that logs “Hello World” to the console. We then assign the “myFunction” function to the “myFunction” property of the window object.

Declaration Merging and Extending Global Types

Declaration merging allows for extending global types like “Window” inside a TypeScript module. This means that you can add new properties and methods to the Window object without modifying the Window object directly. The following code demonstrates how to extend the Window type in TypeScript:

declare global  interface Window  myProp: string; > >declare module "my-module"  interface Window  myNewProp: number; > >window.myProp = "Hello World"; window.myNewProp = 42; 

In this example, we declare a new interface called “Window” and add a new property called “myProp” to it. We then declare a new module called “my-module” and extend the Window interface with a new property called “myNewProp”. We can then access both the “myProp” and “myNewProp” properties of the window object.

Using Namespaces for Logical Grouping of Functionalities

Namespaces allow for logical grouping of functionalities. They can include interfaces, classes, functions, and variables. The following code demonstrates how to use namespaces:

namespace MyNamespace  export const myFunction = () =>  console.log("Hello World"); >; >MyNamespace.myFunction(); 

In this example, we define a new namespace called “MyNamespace” and add a new function called “myFunction” to it. We can then access the “myFunction” function by using the “MyNamespace” namespace.

Accessing the Global Object in Different JavaScript Environments

The global object can be accessed through different syntax in different JavaScript environments. In the web environment, the global object is the window object. In Node.js, the global object is the global object. The following code demonstrates how to access the global object in the web and in Node.js:

// Web const globalObject = window;// Node.js const globalObject = global; 

In this example, we define a new variable called “globalObject” that is assigned the value of the global object in the web and in Node.js. We can then access the global object through the “globalObject” variable.

Important and Helpful Points

• Adding a new property to the window object in TypeScript can be done explicitly by declaring a new interface that extends the Window object.
• Interfaces can be used to create custom interfaces that inherit all the properties and methods of the Window object.
• Webpack may not make all exports available from the window namespace, so it is important to explicitly define exports in code.
• Declaration merging allows for extending global types like “Window” inside a TypeScript module.
• Namespaces allow for logical grouping of functionalities.
• The global object can be accessed through different syntax in different JavaScript environments.

Other helpful code examples for adding objects to the window namespace

In Typescript , in particular, typescrpt add onject to window namespace code sample

declare global < interface Window < MyNamespace: any; >>window.MyNamespace = window.MyNamespace || <>;

Conclusion

In this article, we discussed how to add objects to the window namespace in TypeScript. We covered various topics such as adding new properties to the window object, creating interfaces by extending the Window object, dealing with exports and Webpack, declaration merging and extending global types, using namespaces for logical grouping of functionalities, and accessing the global object in different JavaScript environments. TypeScript is a powerful tool that allows for the creation of more robust and maintainable code. By following the guidelines outlined in this article, you can write better TypeScript code that is more organized and easier to maintain.

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How to declare a new property on the Window object with Typescript

In Javascript, the declaration of a new property within any object, is very simple and there’s even 2 ways to do it:

// Declare programatically window.MyProperty = function()< alert("Hello World"); >; // Declare with Brackets window["MyProperty"] = function()< alert("Hello World"); >;

The Window variable, is an object, therefore to declare a new property in the Window object with Javascript we would just simply use the previous snippet and everything will work like a charm. However, in Typescript that wouldn’t work . at least during the compilation and in your IDE syntax checking (if it supports TypeScript), you should see the following warning:

[TS] Property ‘MyProperty’ does not exist on type ‘Window’

The error indeed, is very simple. To understand it, we are going to use the following TypeScript class, the DeviceInfo class:

class DeviceInfo < setInfo()< console.log("This is just a demo . "); >> let info = new DeviceInfo(); // The following line should throw the error: // Property 'name' does not exist on type 'DeviceInfo' info.name = "BatPhone";

To solve the error, we just need to add the name property to the DeviceInfo class and that’s it:

class DeviceInfo < name: string; setInfo()< console.log("This is just a demo . "); >> let info = new DeviceInfo(); // No more warning ! info.name = "BatPhone";

Very easy to solve in a custom object created by your own, but , the Window is not a class of yours . that’s an already built-in object in the browser! Then, how can you add a new property to the Window object in typescript properly?

Declaring a new property in the Window

Depending on the way you code and the TypeScript version that you use, there are 2 ways to add a new property to the window:

1. With an interface

To add a new property and prevent any compile error, you can use an interface to describe the Window with your new property. In TypeScript, interfaces fill the role of naming types, and are a powerful way of defining contracts within your code as well as contracts with code outside of your project.

As the purpose of an interface is only to describe a type or an object (they won’t be transpiled into Javascript), you can create an interface to describe window and add as a new property, the name of your property and the error shouldn’t appear anymore:

interface Window < MyProperty: any; >window.MyProperty = 12345; // as the type of MyProperty is any, you can change the value // for the value you want, or specify a different type according // to your needs :)

The following examples shows how to declare different properties in the Window object using an Interface with different types:

interface Window < CustomNumber: number; CustomFunction: Function; CustomString: string; CustomAnything: any; >window.CustomNumber = 123; window.CustomFunction = () => < console.log("Hello World"); >; window.CustomString = "TypeScript"; window.CustomAnything = < hello: 12, world: 21 >;

2. Keep your code dynamic

If you don’t want to take care of the types, you can simply use the following syntax to create a new property:

(window).MyPropertyName = "Something";

The following example shows how to declare different types in the window:

(window).CustomFunction = () => < alert("Hello World"); >; (window).CustomNumber = 123; (window).CustomString = "Code";

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How to add a new property to a window object in typescript?

Window is an inbuilt JavaScript global object. It provides properties like location and history and also methods like open . The same can be used in Typescript.

It is a tricky one to add a property in a window object in javascript and typescript

How do you set the new property to a window object in javascript?

Yes, We can add properties, and methods in the window global object as seen below

window.employee = <>; // global Object container; don't use var employee.name = 1; employee.salary = 1; employee.totalSalary = function ()  12 * employee.salary; >; employee.display = function ()  console.log(employee.name); >;

As javascript, there is no type checking, This will work, However, This will not work in typescript and gives the following error.

The property ‘employee’ does not exist on the value of type ‘window’ any:

So adding property in typescript is tricky and can be done with multiple approaches

Custom Interface Extends window object in typescript

Create an interface by extending the Window object. And, Add the properties to this.

First, Let’s Create an interface: EmployeeWindow.ts .

export interface EmloyeeWindow extends Window  name: string; salary: Integer; totalSalary: Function; display: Function; >

Next, Window is a global object namespace, which is not required to import, But a custom interface needs to import in a class you want to use

import  EmloyeeWindow > from "./EmployeeWindow.ts";

The third is to declare a class of type Window object.

declare let window: EmloyeeWindow;

Finally, You can test the same by adding properties to the window object.

window.name = 'Franc'; window.salary = 5000; window.totalSalary = () =>  return window.salary * 12; >; window.display =  console.log(window.name + ' salary is ' + window.totalSalary) >;

Any type in typescript

Please create a variable with the type assertion keyword as , which means the compiler understood and consider this as a window type.

as is a keyword used to infer the type as a new type

let EmployeeWindow = window as any; EmployeeWindow.name = 'Franc'; EmployeeWindow.salary = 5000; EmployeeWindow.totalSalary = () =>  return window.salary * 12; >; EmployeeWindow.display =  console.log(window.name + ' salary is ' + window.totalSalary) >;

Wrap up

Adding a property to a window object in javascript is indeed simple and easy, However, Typescript needs little extra coding and steps required to set the property in the window object.

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