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An ES6 async/promise proof of concept using Proxies.
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/* | |
Using Es6 Proxies, I created an object that can resolve promises from a chained object accessor pattern. | |
simply await the values, or supply a callback to .then() and watch the magic. | |
*/ | |
Symbol.queue = Symbol("queue"); //using Symbols to hide properties from being used or altered | |
Symbol.data = Symbol("data"); | |
function Promiser( obj ) { | |
return new Proxy(obj, { | |
get(target, prop){ | |
var new_prop = false; | |
if(prop == "then" && this[Symbol.queue]){ //if "then" is accessed, and there is something in the queue | |
let resolve = this[Symbol.queue]; | |
let promise = resolve[1]((data)=>{ | |
let obj = this[Symbol.data] //resolved data from last promise | |
obj[resolve[0]] = data; | |
return new Promise((res,rej)=>{ | |
this[Symbol.data] = {}; //erase data | |
delete this[Symbol.queue];//erase queue | |
res(obj);//resolve then | |
if(obj) | |
Object.assign(target, obj ); //Assign resolved values to the proxy target, so that promise wont have to be called again. | |
}) | |
}); | |
let then = promise.then.bind(promise); | |
return then; | |
} | |
let promise; | |
if(target[prop] instanceof Promise == false && prop !== "then"){ //if the prop is not "then" or a promise. (a real value) | |
if(this[Symbol.queue]){ //if there is a queue | |
let resolve = this[Symbol.queue], obj = this[Symbol.data]; | |
promise = resolve[1]((data)=>{ //resolve last promise | |
obj[resolve[0]] = data; | |
return new Promise((res,rej)=>{ //create immediately resolving promise with value | |
res(target[prop]) | |
}) | |
}); | |
promise = promise.then.bind(promise); //bind to keep this | |
}else{ | |
promise = new Promise((res,rej)=>{ //else simply create a new promise with value | |
res(target[prop]) | |
}) | |
promise = promise.then.bind(promise); | |
} | |
} | |
if(this[Symbol.queue]){ //if it is a promise and there is a queue | |
let resolve = this[Symbol.queue], obj = this[Symbol.data]; | |
promise = resolve[1]((data)=>{ //resolve last promise | |
obj[resolve[0]] = data; | |
return target[prop]; //return this promise | |
}); | |
promise = promise.then.bind(promise); //bind | |
} | |
else if (!promise) { | |
this[Symbol.data] = {}; //if there after all the alternations, there is still no promise, erase the data. start from scratch. | |
promise = target[prop].then.bind(target[prop]); | |
} | |
this[Symbol.queue] = [ prop, promise ]; //supply the promise and the property. | |
//all alternations ensure that no matter what the value, a promise is always given which must be resolved. | |
return new Proxy(target, this); | |
} | |
}) | |
} | |
var obj = Promiser({ | |
a: new Promise((res,rej)=>setTimeout(()=>res(1), 1300)), | |
b: new Promise((res,rej)=>setTimeout(()=>res(2), 1300)), | |
c: new Promise((res,rej)=>setTimeout(()=>res(3), 1300)), | |
d:1, | |
e:2, | |
f:3, | |
}); | |
console.log( await obj.a.b.c.f.e ); //prints { a:1, b:2, c:3, f:3, e:2 } |
@tonix-tuft. I’d be elated if you did that. Feel free to add it. Reference would obviously be appreciated.
Thank you! I ended up adding it as a pigretto's builtin, I called it POJOPromiser
(referenced your gist, refactored the code a bit and added a mutateTargetOnSettledPromiseQueue
parameter): https://github.com/tonix-tuft/pigretto/blob/master/src/builtin/POJOPromiser.js .
pigretto is a library I wrote which helps creating proxies using an AOP API. You can use it if you find it useful for your needs, though I haven't documented it yet (it's on my TODO list).
Cheers!
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Pretty cool! May I add this to my js-utl utility library? I will write a
@see
annotation with a link to this gist. Thank you!