How does .JSLIB file work?

Unity Engine
, ,
1

I can’t understand how to work with .jslib files. I don’t understand the syntax of this type of file. Also I couldn’t find any easy explanation of it

The problem started when I tried to make two functions global for all .jslib files:

/**
 * @param {string} str
 * @returns {string}
 */
function StrJSToStrCS (str) {
   const bufferSize = lengthBytesUTF8(str) + 1;
   const buffer = _malloc(bufferSize);
   stringToUTF8(str, buffer, bufferSize);
   return buffer;
}

/**
 * @param {string} str
 * @returns {string}
 */
function StrCSToStrJS (str) {
   return UTF8ToString(str);
}

What I already tried:

  • To define these two functions in the same file
function StrJSToStrCS (str) {
  const bufferSize = lengthBytesUTF8(str) + 1;
  const buffer = _malloc(bufferSize);
  stringToUTF8(str, buffer, bufferSize);
  return buffer;
}
   
function StrCSToStrJS (str) {
  return UTF8ToString(str);
}
   
const lib = {
  Hello: function () {
    return StrJSToStrCS('HELLO WORLD!');
  },

  ConsoleLog: function (str) {
    console.log(StrCSToStrJS(str));
  }
};
   
mergeInto(LibraryManager.library, lib);
  • To define these two functions in script tag in .html after reading this. If it’s important the script tag I inserted at the bottom of body tag
<script>
function StrJSToStrCS (str) {
  const bufferSize = lengthBytesUTF8(str) + 1;
  const buffer = _malloc(bufferSize);
  stringToUTF8(str, buffer, bufferSize);
  return buffer;
}
   
function StrCSToStrJS (str) {
  return UTF8ToString(str);
}
</script>

const lib = {
  Hello: function () {
    return StrJSToStrCS('HELLO WORLD!');
  },

  ConsoleLog: function (str) {
    console.log(StrCSToStrJS(str));
  }
};
   
mergeInto(LibraryManager.library, lib);
  • To define these functions in .jspre file after reading this:
    “the .jspre files are added to the build using the --pre-js option, while the .jslib are added using the --js-library option”
    .jspre file:
function StrJSToStrCS (str) {
  const bufferSize = lengthBytesUTF8(str) + 1;
  const buffer = _malloc(bufferSize);
  stringToUTF8(str, buffer, bufferSize);
  return buffer;
}
   
function StrCSToStrJS (str) {
  return UTF8ToString(str);
}

.jslib file:

const lib = {
  Hello: function () {
    return StrJSToStrCS('HELLO WORLD!');
  },

  ConsoleLog: function (str) {
    console.log(StrCSToStrJS(str));
  }
};
   
mergeInto(LibraryManager.library, lib);
  • To simply define these functions as methods in the same object:
const lib = {
  StrJSToStrCS: function(str) {
    const bufferSize = lengthBytesUTF8(str) + 1;
    const buffer = _malloc(bufferSize);
    stringToUTF8(str, buffer, bufferSize);
    return buffer;
  },
   
  StrCSToStrJS: function(str) {
    return UTF8ToString(str);
  },
       
  Hello: function() {
    return this.StrJSToStrCS('HELLO WORLD!');
  },
       
  ConsoleLog: function(str) {
    console.log(this.StrCSToStrJS(str));
  }
}
   
mergeInto(LibraryManager.library, lib);

But whatever I do, he writes every time in console that StrJSToStrCS/StrCSToStrJS is not defined

I don’t understand at all why the last method doesn’t work. Isn’t lib just a simple object?

Is it possible to make these two functions global for all .jslib files?

2

Functions defined in a .jslib file will have “" prefixed to the function name when compiled. Therefore, call the function name with "” at the beginning.

_StrJSToStrCS('HELLO WORLD!');

However, in the case of SendMessage(), string can be passed as it is without converting it to a pointer, but is there any reason why it is passed as a pointer?

3

Finally I found the answer!

In .jspre file I had to write:

Module.StrJSToStrCS = function(str) {
   const bufferSize = lengthBytesUTF8(str) + 1;
   const buffer = _malloc(bufferSize);
   stringToUTF8(str, buffer, bufferSize);
   return buffer;
}

Module.StrCSToStrJS = function(str) {
   return UTF8ToString(str);
}

and then in .jslib file call these functions like this:

const lib = {
    Hello: function() {
        return gameInstance.Module.StrJSToStrCS('HELLO WORLD!');
    },

    ConsoleLog: function(str) {
        console.log(gameInstance.Module.StrCSToStrJS(str));
    }
}

mergeInto(LibraryManager.library, lib);
4

No, I just didn’t see the argument type error so I didn’t know it :slight_smile:
I edited my question

5

I will try your method. Will these function defined in .jslib file visible in other .jslib files?

6

Even if there are multiple .jslibs, they are all expanded in one scope, so you can call functions defined in other .jslibs.

For example, you can create JSLIBTest_Foo.jslib and JSLIBTest_Bar.jslib as follows and call functions defined in JSLIBTest_Bar from functions defined in JSLIB_Foo.

// JSLIBTEST_Foo.jslib
const foo = {
    JSLIBTest_Foo: function() {
        _JSLIBTest_Bar();
    }
};
mergeInto(LibraryManager.library, foo);

// JSLIBTest_Bar.jslib
const bar = {
    JSLIBTest_Bar: function() {
        console.log('---bar---');
    }
};
mergeInto(LibraryManager.library, bar);

// Test C# Code
using System.Runtime.InteropServices;
using UnityEngine;

public class JSLIBTest : MonoBehaviour
{
    [DllImport("__Internal")]
    private static extern void JSLIBTest_Foo();

    [DllImport("__Internal")]
    private static extern void JSLIBTest_Bar();

    private void Start()
    {
        JSLIBTest_Foo();
    }
}

8690919--1172559--ss_t.png

1 Like
7

So, if you create multiple .jslibs, if you have the same function name in another .jslib, it may be overwritten, so be careful with the function name.

8

Thank you so much! After your words I went to documentation again and saw that at the of note which directly above this sections says exactly what you said. Forgive me for my blindness :slight_smile: