Use of 'extends' keyword in class definition - is it supported?

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•

Gordon

I'm not sure I understand? Are you running with a minifier turned on? The code you posted below has no mention of setPrototypeOf or $jscomp.global.Object so I presume they are being added by something.

Uploading the code in your attached file from the main IDE window:

class Polygon {
  // ..and an (optional) custom class constructor. If one is
  // not supplied, a default constructor is used instead:
  // constructor() { }
  constructor(height, width) {
    this.name = 'Polygon';
    this.height = height;
    this.width = width;
  }
}




class Square extends Polygon {
  constructor(length) {
    // Here, it calls the parent class' constructor with lengths
    // provided for the Polygon's width and height
    super(length, length);
    // Note: In derived classes, super() must be called before you
    // can use 'this'. Leaving this out will cause a reference error.
    this.name = 'Square';
  }

  get area() {
    return this.height * this.width;
  }
}


var pol = new Polygon( 4, 3 );

works perfectly for me on a recent build of Espruino.

•

Robin in reply to @Gordon

Wed 2018.09.26

I'm surprised and disappointed @Gordon that you missed that one. In your code, instance is of base class and not the derived class. It does however show that syntax checking is working. I left in the commented out instantiation lines that followed to show the difference between the two, valid syntax vs run-time, without the need of submitting two files. Was it necessary to add the obvious comment to un-comment the subsequent lines?

re: 'The code you posted below has no mention of setPrototypeOf'

Yes, agreed, and as I mentioned that 'never specified an 'inherits' function' also, so that puzzled me too.

Per your suggestion, when I checked, I had 'Closure Simple Optimizations' turned on, so your presumption is proved. But, that brings up another issue, does this mean the minification process is bad?

I turned off minification and code passes fine, but fails when turned on. And even more puzzling, when I pass the source through

https://closure-compiler.appspot.com

// ==ClosureCompiler==
// @output_file_name default.js
// @compilation_level SIMPLE_OPTIMIZATIONS
// @formatting pretty_print
// ==/ClosureCompiler==

that source compiles with:

Compilation was a success!

Sending that code, default.js, to the device results in the same error as in #1. How does one troubleshoot that type of error? If I understand this correctly, converting the minified code to byte code is where the issue lies.

Use of 'extends' keyword in class definition - is it supported?

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