How to make the 'end' event works in the node.js

Question

I am not understanding why I cannot call the end event in this code below. I have already read too many things about how to do it, and I understand that I need to switch the stream (process.stdin) into a flowing mode. But if I have a data event in my code, isn't it automaticaly in flowing mode? I have already tried process.stdin.resume() and .pipe(). I am runing this on Node.js. Thanks very much.

// begin snippet: js hide: false console: true babel: false 
// language: lang-js

var i=0;
process.stdin.resume();
process.stdin.setEncoding("utf-8");
var stdin_input = "";

process.stdin.on("data", function (input) {
    stdin_input += input;
    i++
    if(i>5){
        //do something to call "end" event at the bottom
        i=0
    }       
});

process.stdin.on("end", function () {
    console.log(stdin_input);
             });
// end snippet