nodejs - how to keep an status at top of stdout - node.js

Question

I'm trying to output something like these:
counter is: 10 <= fixed line and auto updating
console.logs, etc... <= other console.logs, errors, defaul outputs
console.logs, etc...
console.logs, etc...
console.logs, etc...
Is this possible?
I have tried with process.stdout.write() but it is not working.
var counter = 0;
setInterval(function(){
counter++;
process.stdout.write("counter is " + counter + " \r");
}, 500);
setInterval(function(){
console.log('some output');
}, 1500);

Answer 1

Here's an example using blessed:
var blessed = require('blessed');
var screen = blessed.screen(),
body = blessed.box({
top: 1,
left: 0,
width: '100%',
height: '99%'
}),
statusbar = blessed.box({
top: 0,
left: 0,
width: '100%',
height: 1,
style: {
fg: 'white',
bg: 'blue'
}
});
screen.append(statusbar);
screen.append(body);
screen.key(['escape', 'q', 'C-c'], function(ch, key) {
return process.exit(0);
});
function status(text) { statusbar.setContent(text); screen.render(); }
function log(text) { body.insertLine(0, text); screen.render(); }
var c = 1;
setInterval(function() {
status((new Date()).toISOString());
log('This is line #' + (c++));
}, 100);
Here's a simpler example that has almost the same effect (the status bar doesn't fill in extra space with background color):
var screen = blessed.screen(),
body = blessed.box({
top: 0,
left: 0,
width: '100%',
height: '100%',
tags: true
});
screen.append(body);
screen.key(['escape', 'q', 'C-c'], function(ch, key) {
return process.exit(0);
});
function status(text) {
body.setLine(0, '{blue-bg}' + text + '{/blue-bg}');
screen.render();
}
function log(text) {
body.insertLine(1, text);
screen.render();
}
var c = 1;
setInterval(function() {
status((new Date()).toISOString());
log('This is line #' + (c++));
}, 100);

Answer 2

Aside there are a lot of node modules that can help you do this,(blessed, ncurses, ansi, termhelper), for educational purposes you can also do it with vanilla node easily using process.stdout.moveCursor:
var logs = [];
function log(text) {
logs.push(text);
console.log(text);
}
function changeCounter(n) {
process.stdout.moveCursor(0, -logs.length - 1);
printCounter(n);
logs.forEach(function (log) { console.log(log) });
}
function printCounter(n) {
console.log('Counter is:', n);
}
// Now lets test
printCounter(0);
var i = 1;
setInterval(function () {
log('meoww');
changeCounter(i++);
});
Though you have to write to extra code to prevent overflowing terminal.

Answer 3

A traditional library for doing that sort of thing (drawing text at other than the bottom of the screen) is "curses"...there are bindings for Node.js but there is also "blessed" (ha ha) which looks easier to use: https://github.com/chjj/blessed