Meteor wrapAsync and this

Calling wrapAsync on a function will not propagate the value of this from the resulting function to the wrapped function. But the behaviour may be emulated by transforming it into an actual parameter.

The emulation procedure involves transforming this into a parameter, then calling wrapAsync and finally moving the parameter back to the function context. The mentioned process can be achieved with the following composing of functions:


There are a couple of complementary functions to define before the composing function may be used, namely thisToParam and paramToThis. The respective implementations are shown below.

function thisToParam(targetFn) {
  return function (...args) {
    return targetFn(this, ...args);
function paramToThis(targetFn) {
  return function (_this, ...args) {
    return targetFn.apply(_this, args);