immediato/dist/index.js

An isomorphic setImmediate implementation that doesn't prevent the process from exiting naturally.

/* HELPERS */
let callbacksId = 0;
let callbacksExecuting = false;
let callbacksMap = new Map();
let { port1, port2 } = new MessageChannel();
/* MAIN */
const setImmediate = (callback, ...args) => {
    const callbackId = (callbacksId += 1);
    const callbackWithArgs = () => callback(...args);
    callbacksMap.set(callbackId, callbackWithArgs);
    port1.onmessage = runImmediate;
    port2.postMessage(callbackId);
    return callbackId;
};
const clearImmediate = (callbackId) => {
    callbacksMap.delete(callbackId);
    if (callbacksMap.size)
        return;
    port1.onmessage = null; // Important to reset this, as it will ~hang the process otherwise
};
const runImmediate = (event) => {
    const callbackId = event.data;
    const callback = callbacksMap.get(callbackId);
    if (!callback)
        return;
    if (callbacksExecuting) {
        setTimeout(runImmediate, 0, callbackId);
    }
    else {
        try {
            callbacksExecuting = true;
            callback();
        }
        finally {
            callbacksExecuting = false;
            clearImmediate(callbackId);
        }
    }
};
/* EXPORT */
export { setImmediate, clearImmediate };