Promisifying Level, issue with encodeLtgt?

Hey guys,

Not sure if this really is the proper place to ask, but I’ll try anyway (unless you guys have a Discord or Slack server).

I’m attempting to promisify level in my own way - the existing then-level isn’t actually working, a few issues pushed me to work on my own version, which also happens to support node 8 native promisifying using the util module.

The full code is gisted here. The issue I have specifically is when attempting to create a createKeyStream.

Code:

const lp = new LevelPromise('hallo');

const test = async() => {
  await lp.put('hallo', 'hehe');
  const rv = await lp.get('hallo');
  console.log(rv);
  
  const output = [];
  lp.createKeyStream()
    .on("data", key => lp.get(key).then(d => output.push(JSON.parse(d))))
    .on("end", () => console.log(output));
  
  //await lp.close();
  //lp.destroy();
}

test();

Resulting Error:

Uncaught Promise Error:  TypeError: Cannot read property 'encodeLtgt' of undefined
    at LevelPromise.LevelUP.readStream.LevelUP.createReadStream (/root/level-promise/node_modules/levelup/lib/levelup.js:323:24)
    at LevelPromise.LevelUP.keyStream.LevelUP.createKeyStream (/root/level-promise/node_modules/levelup/lib/levelup.js:336:15)
    at test (/root/level-promise/index.js:61:6)
    at <anonymous>

I’m not having this issue without the promisify stuff, createKeyStream works correctly.

[ralphtheninja]

this[key] = (...args) => this.level[key](...args);

Now you’re binding 😉 This should be the same as doing

this[key] = this.level[key].bind(this.level);

[vweevers]

However, vmweevers put me on the right track: this[key] = prototype[key]; doesn’t work for… honestly I’m not exactly sure, the exact inner workings of javascript are sometimes a little beyond me.

Credit goes to @ralphtheninja 💘

@eslachance The reason that this[key] = prototype[key] doesn’t work is because in JavaScript the value of this is determined by how a function is called.