What are some creative ways to utilize postMessage instead of relying on nextTick or setTimeout with a zero millisecond delay?

Question

What are some creative ways to utilize postMessage instead of relying on nextTick or setTimeout with a zero millisecond delay?

I just came across a theory that postMessage in Google Chrome is similar to nextTick. This idea somewhat confused me because I was under the impression that postMessage was primarily used for communication between web workers.

Experimenting with expressions like

postMessage(function() {return;});

, I realized it doesn't schedule a function to run when the event loop is idle, but instead returns an error. It appears that postMessage strictly accepts a message as input.

Is there a way to leverage postMessage for scheduling function calls during idle times in the event loop?

javascript

Answer 1

Answer №1

Google Chrome utilizes the V8 engine, which includes a microtask queue concept. The use of postMessage is part of the DOM API and functions similarly to nextTick in Node.js (although their loop cycles differ).

There's an old workaround that employs postMessage to mimic a setTimeout(fn, 0), as shown below:

var queue = [];
window.addEventListener("message", function(e){
    if((e.source !== window) || (e.data === "flush")) return; // incorrect message
    queue.forEach(function(fn){ fn(); }); // execute all functions;
    queue = []; // clear the queue;
});

function nextTick(fn){
    queue.push(fn); // add the function
    window.postMessage(fn, "flush", "*");
}

Although more intricate methods using MessageChannel exist, the underlying principle remains the same.

You can read about this technique in an older blog post here, although it's not commonly used anymore due to a quicker hack utilizing mutation observers for faster setTimeout.

For more modern approaches, refer to this source.

Answer 2

Google Chrome utilizes the V8 engine, which includes a microtask queue concept. The use of postMessage is part of the DOM API and functions similarly to nextTick in Node.js (although their loop cycles differ).

There's an old workaround that employs postMessage to mimic a setTimeout(fn, 0), as shown below:

var queue = [];
window.addEventListener("message", function(e){
    if((e.source !== window) || (e.data === "flush")) return; // incorrect message
    queue.forEach(function(fn){ fn(); }); // execute all functions;
    queue = []; // clear the queue;
});

function nextTick(fn){
    queue.push(fn); // add the function
    window.postMessage(fn, "flush", "*");
}

Although more intricate methods using MessageChannel exist, the underlying principle remains the same.

You can read about this technique in an older blog post here, although it's not commonly used anymore due to a quicker hack utilizing mutation observers for faster setTimeout.

For more modern approaches, refer to this source.

What are some creative ways to utilize postMessage instead of relying on nextTick or setTimeout with a zero millisecond delay?

Answer №1

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