Uncaught reference to defined model within extension class.

I’m trying to use predict() to return predictions from my tensorflow model. within a scratch extension My code is as follows:

importModel() {
        console.log("import model start");
        //from https://github.com/googlecreativelab/teachablemachine-community/blob/master/libraries/image/README.md
        //also https://medium.com/jspoint/javascript-promises-and-async-await-as-fast-as-possible-d7c8c8ff0abc
        const url = <URL>;
        const modelUrl = url + "model.json";
        const metadataUrl = url + "metadata.json";
        //https://github.com/LLK/scratch-vm/issues/2914#issuecomment-791514353
        return tmImage.load(modelUrl, metadataUrl)
            .then((model) => {
                console.log(model);
                maxPredictions = model.getTotalClasses();
            });
    }
    getXCoord() {
        //A1 or A2 returns 0
        //B1 or B2 returns 1
        const prediction = model.predict(this.runtime.renderer._allDrawables[target.drawableID]);
    }

model and maxPredictions are global variables defined by let model, labelContainer, maxPredictions;. However, when I run my code, getXCoord throws the following error: Uncaught TypeError: Cannot read property 'predict' of undefined.

If I try the following:

getXCoord() {
        //A1 or A2 returns 0
        //B1 or B2 returns 1
        model = importModel();
        const prediction = model.predict(this.runtime.renderer._allDrawables[target.drawableID]);
    }

It returns index.js:117 Uncaught ReferenceError: importModel is not defined. However, importModel is in the class and is clearly defined.

[adroitwhiz]

In JavaScript, anonymous functions (like the one in your promise callback) bind the this value to window.

If you want this to refer to the extension class, you need to use an arrow function, which does not bind this:

            .then(model => {
                const prediction = model.predict(this.runtime.renderer._allDrawables[target.drawableID]);
                console.log(prediction);
            });

[MarkKocherovsky]

Do I need to pass args, util and leave the arguments empty?

In JavaScript, function arguments are passed by position–it doesn’t matter what you name them. So yes, the first argument, which you’ve named “util”, will be what other blocks name args. You need the function signature to be args, util.

Note that this will only work if getXCoord is a function corresponding to a block. If getXCoord is a utility function called by other block functions, then you’ll need to pass the proper arguments yourself.

Once again, if you need help understanding more general JavaScript behavior like how function arguments work, you should probably look to other JavaScript learning resources rather than asking open-source maintainers to teach you JavaScript on a bug tracker.

Alright, the function is nearly working. I’m still getting a JS error, but I’m not sure it’s due to Scratch. Again, I’d like to thank everyone for their assistance; it means a lot to me!