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Set up your JavaScript plug-in

Create a JavaScript plug-in that your Unity project can interact with.
Read time 3 minutesLast updated 12 days ago
You can call functions from your JavaScript plug-ins in your Unity projects. Unity supports two JavaScript plug-in file types that let you add JavaScript code to your Unity project:
  • .jslib
  • .jspre
Note
Unity currently supports ECMAScript 5 (ES5) syntax in .jslib and .jspre files. ES6 syntax isn't yet supported.
If you want to call functions from C++ plug-ins instead, refer to Call C/C++/C# functions from Unity C# scripts.

Import your JavaScript files into your Unity project

The recommended way to use browser JavaScript in your project is to add your JavaScript sources (.jspre and .jslib files) to your project, and then use those functions or libraries directly in your Unity C# script code.
Place your JavaScript plug-in files in any folder, such as 
Assets/JSPlugins
.
If your JavaScript plug-in isn't compatible with all Unity or Emscripten versions, you can specify a compatible version range. These incompatibilities often occur because of breaking changes in the browser interaction code. To set a compatible version range, use the Minimum Unity Version, Maximum Unity Version, Minimum Emscripten Version, and Maximum Emscripten Version settings in the Inspector window. Add a separate version of the plug-in for each compatible range, and Unity selects the correct version at build time.

Settings for a JavaScript plug-in on the Web platform.

Call functions from the .jslib file type

You can call functions from your .jslib plug-in files in your Unity C# or native scripts.
The .jslib file type uses the 
--js-library
Emscripten module. For more information, refer to the Emscripten documentation about the --js-library Emscripten option.
The following code shows an example of a .jslib plug-in file with the ideal syntax that defines some functions (
Hello
and 
HelloString
).
mergeInto(LibraryManager.library, {  Hello: function () {	window.alert("Hello, world!");  },  HelloString: function (str) {	window.alert(UTF8ToString(str));  },});
You can then call these functions in your Unity C# code:
using UnityEngine;using System.Runtime.InteropServices;public class NewBehaviourScript : MonoBehaviour {    [DllImport("__Internal")]    private static extern void Hello();    [DllImport("__Internal")]    private static extern void HelloString(string str);    void Start() {        Hello();        HelloString("This is a string.");    }}
For a full example of code interactions between Unity C# and JavaScript functions, refer to Code examples: Call JavaScript and C/C++/C# functions in Unity.
For more information about interactions between Unity C# and JavaScript, refer to Call JavaScript functions from Unity C# scripts.

Include JavaScript libraries with the .jspre file type

Use the .jspre plug-in file type to include existing JavaScript libraries in your JavaScript code. You can’t use Unity code to interact with the .jspre files, but you can use them in the .jslib code.
The .jspre file type uses the 
--pre-js
Emscripten option. For more information, refer to the Emscripten documentation about the --pre-js Emscripten option.
During the build process, Emscripten creates the 
*.framework.js
file and copies the contents of the .jspre file into the start of the 
*.framework.js
file. This process is useful because all the code is combined into one file so it's easier to manage the files and the code benefits from Emscripten optimizations.

Additional resources