Nodejs event loop: setTimeout v.s. setImmediate v.s. process.nextTick

test.js

const fs = require("fs");

// The execution order of the setTimeout and setImmedate callbacks are non-deterministic.
setTimeout(() => {
    console.info("setTimeout in main");
}, 0);

setImmediate(() => {
    console.info("setImmediate in main");
});

fs.readFile(__filename, () => {
    // When the Event Loop is in the I/O phase, setImmediate callbacks will always executed before setTimeout callbacks
    // since the next phase will be "check" phase where the setImmediate callbacks are queued.
    console.info("readFile");

    setTimeout(() => {
        console.info("setTimeout in I/O");
    }, 0);

    setImmediate(() => {
        console.info("setImmediate in I/O");
    });

    // nextTick callbacks are always processed immediately after the current operation is completed
    process.nextTick(() => {
        console.info("nextTick");
    });
});