jacobRothstein proxy promise thing https://twitter.com/jacobrothstein/status/1201641829269000192

proxyPromise.js

function proxyPromise(promise) {
  const acc = [];

  function createFnProxy(prop) {
    return function(...args) {
      acc.push([prop, args]);

      return proxy;
    };
  }

  const proxy = new Proxy(promise, {
    get(obj, prop) {
      return createFnProxy(prop);
    },
  });

  function cycle(_promise) {
    return _promise.then((resolution) => {
      if (!acc.length) {
        return _promise;
      }

      const [prop, args] = acc.shift();
      const resolutionResult = resolution[prop](...args);
      return cycle(
        resolutionResult && resolutionResult.then
          ? resolutionResult
          : Promise.resolve(resolutionResult)
      );
    });
  }

  cycle(promise);

  return proxy;
}

function main() {
  const promise1 = Promise.resolve({
    x(...args) {
      console.log('[promise1] x called with %o', args);
      return {
        y(...args2) {
          console.log('[promise1] y called with %o', args2);
          return {
            z(...args3) {
              console.log('[promise1] z called with %o', args3);
              return null;
            },
          };
        },
      };
    },
  });

  const promise2 = new Promise((resolve, reject) => {
    const obj = {
      x(...args) {
        console.log('[promise2] x called with %o', args);
        return obj;
      },
      y(...args) {
        console.log('[promise2] y called with %o', args);
        return obj;
      },
      z(...args) {
        console.log('[promise2] z called with %o', args);
        return obj;
      },
    };
    resolve(obj);
  });

  const proxy1 = proxyPromise(promise1);

  proxy1
    .x()
    .y('a')
    .z('foo', 'bar');

  const proxy2 = proxyPromise(promise2);

  proxy2
    .x()
    .y('a')
    .z('foo', 'bar');
}

main();

$ node proxyPromise.js
[promise1] x called with [ [length]: 0 ]
[promise2] x called with [ [length]: 0 ]
[promise1] y called with [ 'a', [length]: 1 ]
[promise2] y called with [ 'a', [length]: 1 ]
[promise1] z called with [ 'foo', 'bar', [length]: 2 ]
[promise2] z called with [ 'foo', 'bar', [length]: 2 ]