javascript - Node: fs write() doesn't write inside loop. Why not? -

i want create write stream , write data comes in. however, able create file nothing written it. eventually, process runs out of memory.

the problem, i've discovered i'm calling write() whilst inside loop.

here's simple example:

'use strict'  var fs = require('fs'); var wstream = fs.createwritestream('myoutput.txt');  (var = 0; < 10000000000; i++) {     wstream.write(i+'\n'); }  console.log('end!') wstream.end(); 

nothing ever gets written, not hello. why? how can write file within loop?

the problem aren't ever giving chance drain buffer. buffer gets full , run out of memory.

writestream.write returns boolean value indicating if data written disk. if data not written, should wait drain event, indicates buffer has been drained.

here's 1 way of writing code utilizes return value of write , drain event:

'use strict'  var fs = require('fs'); var wstream = fs.createwritestream('myoutput.txt');  function writetostream(i) {   (; < 10000000000; i++) {     if (!wstream.write(i + '\n')) {       // wait drain start writing data left off       wstream.once('drain', function() {         writetostream(i + 1);       });       return;     }   }   console.log('end!')   wstream.end(); }  writetostream(0);