Micobit sends serial data to computer only within an event?

Question

I wanna send data from microbit to PC. All the connections work fine. However I find that data is only sent to the computer if the serial write function is written within an event, for example, I use Makecode, and the following two work:

input.onButtonPressed(Button.B, () => {
    serial.writeLine("data from micro:bit!")
})

basic.forever(function () {
    serial.writeLine("data from micro:bit!")
})

However if I just write one line like this, it doesn't work:

 serial.writeLine("data from micro:bit!")

I suspect that the serial write function has to be triggered by something, likely a callback or loop etc? But it seems that the micropython one doesn't have such problem.

Some more background, I'm using Windows 10 and I use the Node.js serialPort package to receive the message. I'm not sure if the environment will affect the behavior.

I appreciate if someone here can share some experience, thank you very much.