Resolve array of promises one after another

Question

I've found lots of solutions for this, typically something like

const serial = funcs =>
  funcs.reduce((promise, func) =>
    promise.then(result =>
      func().then(Array.prototype.concat.bind(result))),
  Promise.resolve([])
  )

I'm trying to map an array of promises and run them one after another,

 serial(Object.keys(tables).map(key => 
 websocketExecute(store,dropTableSQL(tables[key]),null)))
 .then(data => {console.log(data);success(data)})

They all run however I get an error TypeError: func is not a function

And the final then isn't resolved..

Any idea how I run a final .then() on a list of promises?

Answer 1

Your function serial expects its argument to be an array of functions that return Promises

however,

Object.keys(tables).map(key => websocketExecute(store,dropTableSQL(tables[key]),null))

returns an array of the results of calling

websocketExecute(store,dropTableSQL(tables[key]),null)

Which is not likely to be a function returning a promise, more like some result

What you'll want to do is:

serial(Object.keys(tables).map(key => () => websocketExecute(store,dropTableSQL(tables[key]),null)))
.then(data => {console.log(data);success(data)})

Assuming websocketExecute returns a Promise

So now, the array returned by .map is an array of

() => websocketExecute(store,dropTableSQL(tables[key]),null)

Which will get called in turn in .reduce