Question

The following program will hang in NodeJS, does anybody know why?

ended = false;

events = require('events');
eventEmitter = new events.EventEmitter();
eventEmitter.on('end', function() {
  ended = true;
});
setTimeout(function() {
  eventEmitter.emit('end');
}, 100);

while (!ended) {
  process.nextTick();
}

console.log('ended');

Answer 1

nextTick isn’t some kind of yield operation, it’s for scheduling a callback to be called the next time the engine is free to do so. It’s “hanging” because the while loop’s exit condition is never satisfied (and can never be, with that code).