Using a 3rd party js file with TypeScript

Question

I am new to typeScript and I want to be able to use a 3rd party library that does not have definition file. Does typescript allow you to use the external libraries?

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Answer 1

Out of the pragmatic but perhaps not quite kosher categoy, a less elegant and non-TypeScript approach would be to simply declare but not assign the variable/function you want to use with TypeScript. This does not give you Intellisense, but it does allow you to very quickly use the library without creating any declarations or roll your own d.ts file.

For instance, here's an Angular example to provide OidcTokenManager as a constant on an app.core module:

((): void => {
    angular
        .module('app.core')
        .constant('OidcTokenManager', OidcTokenManager);

})();

This will generate a TS2304 - Cannot find name 'OidcTokenManager' TypeScript error.

However, by simply declaring OidcTokenManager as of type any, TypeScript will let you pass:

((): void => {    
    let OidcTokenManager: any;   

    angular
        .module('app.core')
        .constant('OidcTokenManager', OidcTokenManager);

})();

Answer 2

Another way to call external libraries in typescript without compiling error is to use the window"myglobalfunction" notation.

For example:

jQuery call: window["$"]
fileSaver.js : window["saveAs"](blob, "hello world.txt");

etc...

These calls inside typescript don't generate compilation errors, but they are full functioning ways to call the same standard functions.

Answer 3

Does typescript allow you to use the external libraries?

Very easily. You just need to tell typescript about it. lets look at your case.

The library i am trying to use is filesaver.js

Simple just one function saveAs. The simplest declaration:

declare var saveAs:any; 

and now the following will compile just fine:

declare var saveAs:any; 
var blob = new Blob(["Hello, world!"], {type: "text/plain;charset=utf-8"});
saveAs(blob, "hello world.txt");

To write more advanced declrations take a look at: https://github.com/Microsoft/TypeScript-Handbook/blob/master/pages/declaration%20files/Introduction.md

Note

A more exact but possibly overly restrictive sample :

declare function saveAs(data:Blob , filename:string );
var blob = new Blob(["Hello, world!"], {type: "text/plain;charset=utf-8"});
saveAs(blob, "hello world.txt");