Not all lines are cleared, when the number of lines exceeds console height

[ngocdaothanh]

Example program:

const ora = require('ora');

let count = 1;

const spinner = ora(`Line ${count}`);

spinner.start();

setInterval(() => {
  count++;
  spinner.text += `\nLine ${count}`;
}, 50);

setTimeout(() => {
  spinner.succeed();
  process.exit();
}, 1000);

Resize console window to have only 8 lines (I'm using the default Terminal on Mac).

The last 8 lines seem good:

Line 14
Line 15
Line 16
Line 17
Line 18
Line 19
Line 20
mycomputer $ 

But when you scroll up to see all lines, they look like this:

mycomputer $ node index.js 
⠦ Line 1
Line 2
⠧ Line 1
Line 2
Line 3
⠇ Line 1
Line 2
Line 3
Line 4
Line 5
⠏ Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
⠋ Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
⠙ Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10
⠹ Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10
Line 11
✔ Line 1
Line 2
Line 3
Line 4
Line 5
Line 6
Line 7
Line 8
Line 9
Line 10
Line 11
Line 12
Line 13
Line 14
Line 15
Line 16
Line 17
Line 18
Line 19
Line 20
mycomputer $ 

[ngocdaothanh]

ora spinner works by removing previously rendered lines at every frame.
When the number of lines exceed the console height,
ora cannot remove lines above the console top line.
When users scroll up the console, they will see garbage lines.