How to wait for a stream to finish piping? (Nodejs)

Without async/await, it's quite nasty. With async/await, just do this:

Promise.all(promises).then(async (responses) => {  for (...) {    await new Promise(fulfill => stream.on("finish", fulfill));    //extract the text out of the PDF  }})

Something like the following would also work. I use this pattern fairly often:

let promises = [];promises.push(promise1);promises.push(promise2);promises.push(promise3);function doNext(){  if(!promises.length) return;  promises.shift().then((resolved) =>{    if(resolved.property === something){      ...      doNext();    }else{      let file = fs.createWriteStream('./hello.pdf');      let stream = resolved.pipe(file);      stream.on('finish', () =>{        ...        doNext();      });    }  })}doNext();

or break up the handler to a controller and Promisified handler:

function streamOrNot(obj){  return new Promise(resolve, reject){    if(obj.property === something){      resolve();      return;    }    let file = fs.createWriteStream...;    stream.on('finish', () =>{      ...      resolve();    });  }}function doNext(){  if(!promises.length) return;  return promises.shift().then(streamOrNot).then(doNext);}doNext()

You can write the else part inside a self invoked function. So that the handling of stream will happen in parallel

(function(i) {    let file = fs.createWriteStream('./hello.pdf');    let stream = responses[i].pipe(file);  /*     I WANT THE PIPING AND THE FOLLOWING CODE      TO RUN BEFORE NEXT ITERATION OF FOR LOOP  */    stream.on('finish', () => {      //extract the text out of the pdf      extract(filePath, {splitPages: false}, (err, text) => {      if (err) {        console.log(err);      }       else {        arrayOfDocuments[i].text_contents = text;      }    });  });    })(i) 

Else you can handle the streaming part as part of the original/individual promise itself.

As of now you are creating the promise and adding it to array, instead of that you add promise.then to the array(which is also a promise). And inside the handler to then you do your streaming stuff.