Update more than just the last line of output

Question

I know how I can update the last line of output (answered here).

I've noticed though that some programs update more than just the last line.

Here is an example from yarn's output:

All the waiting... lines have a "rotating dot" at the beginning of them, none of which is in the last line.

How can one achieve this?

Devansh J · Accepted Answer · 2018-04-22T11:37:03.453

You can use ANSI Escape sequences to move the cursor...

Example : printing "\033[3A" will make the cursor move three lines up

If I have understood what you want... This should help:

var writeEscape = a => process.stdout.write("\033[" + a);
var moveUp = n => writeEscape(n +"A")
var moveDown = n => writeEscape(n + "B")
var moveRight = n => writeEscape(n +"C")
var moveLeft = n => writeEscape(n + "D")
var waitFor = n => new Promise(r => setTimeout(r,n))

writeEscape("25l"); // hide cursor use writeEscape("","25h") to show it again
process.stdout.write("waiting\n")
process.stdout.write("some other text");
moveUp(1)
moveLeft(15) // "some other text".length = 15

var printWaiting = async() => {
    writeEscape("K"); // erase the whole line

    process.stdout.write("waiting")

    await waitFor(1000)
    process.stdout.write(".")

    await waitFor(1000)
    process.stdout.write(".")

    await waitFor(1000)
    process.stdout.write(".")

    moveLeft(10) // "waiting".length = 7, "...".length = 3

    await waitFor(1000)
    printWaiting()
}
printWaiting();

I have used async/await functions... But setTimeout only will also work...

Update more than just the last line of output

1 Answers1