javascript - 检测链接函数的结束？

Question

Today I'm working on a pet project using chained function calls, and I'm curious how I might detect when the last function in the chain is executed. For example:

func1('initial data').func2().func3().func4();

And after func2-4 have finished working on 'initial data' I'd like to detect when func4 is done. Since func4() isn't always the last function in the chain, aka it could end at .func3() or .func5() for example, or I could mix my function calls up depending on what I'm trying to do, I'm trying to think of a way to detect no more function calls are being done but I'm not getting very far.

Answer 1

You can't.

Besides, if they are not chained:

var v = func1('initial data');
v = v.func2();
v = v.func3();
v = v.func4();

What would you consider to be the last function? Every function is the last function in it's own chain, but if you finalise something after each step, that won't work.

Just make a function that you call last to finalise the process.

Answer 2

The traditional approach is to put whatever you want done after the final function on the next line:

func1('initial data').func2().func3().func4();
allFunctionsDone();

;)

Answer 3

You can write the sequencer, which will help you to do this for you. Instead of executing direct calls, shift the names of the functions and call them one by one. Something like this

executeSequence(func1('init_dat'),[
    'func2',
    'func3',
    'func4'
]);

Answer 4

they on supabase-js can do that magic. but it will make your function chain is asynchronous.

how? just simply implements Promise-like function chain. in this case, I will use class instead.

class Counter {
  constructor() {
    this.count = 0;
  }

  // here's the magic
  then(resolve) {
    console.log(this.count);
    resolve();
  }

  add() {
    this.count++;
    return this;
  }
}

you do still need run last chain function.

new Counter().add().then();

but, you also can do this way.

await new Counter().add();

you also can make it to have return value

then(resolve) {
  resolve(RETURN_GOES_HERE);
}

this method is best to use imo if your function chain is asynchronous.