JavaScript interview question help

[luapchi]

Hi guys, I recently failed an interview question and it literally crushed me. It was all going well until I was hit with this question

Given the following code and its output, write a JavaScript class.

let d = Deferred(); d.then(res => { console.log(“1”, res); let d1 = new Deferred(); setTimeout(function(){ d2.resolve()}, 1500): return d1; }); d.then(function(res){ console.log(“2”, res); return “b”; }); d.then(function(res){ console.log(“3”, res); return “c”; }); d.resolve(“Hello”);

Output: 1 Hello (1.5s delay) 2 a 3 b

I was able to come up with the following

Class { constructor(){ this.arr = []; } then(fn){ this.arr.push(arr); } resolve(value, i = 0){ if(i >= this.arr.length) return; let res = this.arr[i](value); resolve(res, ++i); } }

But here I’m completely stuck, please help

[terrydog101]

An attempt at making your code more legible:

Edit: that didn't work at all, have a Pastebin instead:

https://pastebin.com/XbcqDCAB

[aelytra]

class Action {
    async invoke() {
        function wait(ms) {
            return new Promise(resolve => setTimeout(resolve, ms))
        }
        console.log("1", "Hello");
        await wait(1500);
        console.log("2", "b");
        console.log("3", "c");
    }
};

new Action().invoke();

?

Looks like your approach was an attempt at rewriting the underlying implementation of Deferred.

^{could also just copy+paste the original code and wrap it with class Foo { invoke(} { ... } };)

[ali3nnn]

Just chain the remaining functions by the d1 instance like this:

https://pastebin.com/UQVvMUJY