Node.js "on" function - What does it do?

Question

 var rd = readline.createInterface({
    input: fs.createReadStream(file),
    output: process.stdout,
    terminal: false
});

rd.on('line', function(line) {

And is any way how to make "on" working synchronous. Code inside "on" loop need to be done before executing loop again. Is any way how to do that?

Answer 1

Generally, the on function registers an event handler for a specific event.

The readline::line event serves for this purpose:

Emitted whenever the input stream receives a \n, usually received when the user hits enter, or return. This is a good hook to listen for user input.

— NodeJS documentation

By the way, which keywords did you use for your search? I used nodejs readline.createInterface and the first result was this NodeJS documentation page!