navigator.scheduling is an experimental Navigator entry point for a Scheduling object. Learn what it returns, how isInputPending() helps keep pages responsive, why the Scheduler API is preferred, five examples, and try-it labs.
Read-only property
Scheduling
Experimental
isInputPending()
Stay responsive
Scheduler API
Long JavaScript loops can freeze the UI: clicks and key presses wait until your script finishes. Scheduling helpers let you ask: is the user trying to interact right now?
Reading navigator.scheduling gives you a Scheduling object. Its main method, isInputPending(), returns true when pending input events sit in the event queue.
While you process a big task list, check for pending input. If the user is interacting, pause briefly (yield) so the browser can handle the click or key, then continue.
Learn this API for understanding responsiveness techniques — and know that newer Scheduler features are the preferred direction for new code.
scheduling Propertynavigator.scheduling is not a Boolean. It is an object that exposes scheduling helpers for the current document.
mousemove / wheel.Scheduler when available.General form of the property:
navigator.schedulingScheduling object (when supported).// Always feature-detect first
if (
"scheduling" in navigator &&
typeof navigator.scheduling.isInputPending === "function"
) {
const pending = navigator.scheduling.isInputPending();
console.log("input pending?", pending);
// Optional: include continuous events (mousemove, wheel, …)
const pendingContinuous = navigator.scheduling.isInputPending({
includeContinuous: true
});
console.log("pending (incl. continuous)?", pendingContinuous);
} else {
console.log("navigator.scheduling is not available.");
}
// Prefer Scheduler when present (modern alternative)
if (globalThis.scheduler && typeof scheduler.yield === "function") {
// await scheduler.yield();
}| Goal | Code |
|---|---|
| Get Scheduling object | navigator.scheduling |
| Feature detect | "scheduling" in navigator |
| Pending input? | navigator.scheduling.isInputPending() |
| Include continuous events | isInputPending({ includeContinuous: true }) |
| Returns | true / false |
| Modern alternative | scheduler.yield() / postTask() |
| Status (MDN) | Experimental |
Four facts to remember about navigator.scheduling.
SchedulingAPI entry point
experimentalNot Baseline
isInputPendingboolean check
SchedulerNewer API
scheduling vs Scheduler vs Blind Yieldingnavigator.scheduling | scheduler (Scheduler API) | setTimeout(0) only | |
|---|---|---|---|
| Maturity | Experimental; superseded path | Preferred for new scheduling work | Widely available |
| Idea | Yield when input is pending | Explicit yield / prioritized tasks | Yield at fixed intervals |
| Best for | Learning / legacy Chromium demos | Modern responsive task runners | Simple fallback everywhere |
Every example feature-detects first. Prefer Try It Yourself — results depend on browser support and whether input is pending at that moment.
Detect the API and read a single pending-input check.
schedulingAlways check support before using the property.
const hasScheduling = "scheduling" in navigator;
const hasMethod =
hasScheduling &&
typeof navigator.scheduling.isInputPending === "function";
console.log("scheduling in navigator: " + hasScheduling);
console.log("isInputPending available: " + hasMethod);Sample output shows a supporting Chromium browser. Others may print false.
isInputPending()Ask once whether input is waiting right now.
if (
"scheduling" in navigator &&
typeof navigator.scheduling.isInputPending === "function"
) {
const pending = navigator.scheduling.isInputPending();
console.log("isInputPending(): " + pending);
} else {
console.log("navigator.scheduling is not available.");
}Idle pages usually return false. Clicking while a long script runs can flip it to true.
Continuous events, a mini task runner, and the Scheduler fallback.
includeContinuous OptionOptionally count continuous events like mouse move and wheel.
if (
"scheduling" in navigator &&
typeof navigator.scheduling.isInputPending === "function"
) {
const discrete = navigator.scheduling.isInputPending();
const continuous = navigator.scheduling.isInputPending({
includeContinuous: true
});
console.log("default: " + discrete);
console.log("includeContinuous: " + continuous);
} else {
console.log("navigator.scheduling is not available.");
}MDN: includeContinuous defaults to false. Set true to treat continuous trusted events as pending input.
Simplified version of MDN’s task-runner idea.
function yieldToMain() {
return new Promise(function (resolve) {
setTimeout(resolve, 0);
});
}
async function runTasks(tasks) {
while (tasks.length > 0) {
const canCheck =
"scheduling" in navigator &&
typeof navigator.scheduling.isInputPending === "function";
if (canCheck && navigator.scheduling.isInputPending()) {
await yieldToMain();
continue;
}
const task = tasks.shift();
task();
}
}
runTasks([
function () { console.log("task A"); },
function () { console.log("task B"); },
function () { console.log("task C"); }
]).then(function () {
console.log("done");
});With no pending input, tasks run back-to-back. If input arrives mid-loop, the runner yields so the UI can respond.
Scheduler When AvailableDetect both APIs and choose the modern path first.
const lines = [];
if (globalThis.scheduler && typeof scheduler.yield === "function") {
lines.push("Scheduler.yield: available — prefer this for new code");
} else {
lines.push("Scheduler.yield: missing");
}
if (
"scheduling" in navigator &&
typeof navigator.scheduling.isInputPending === "function"
) {
lines.push(
"navigator.scheduling.isInputPending: available — experimental / legacy path"
);
} else {
lines.push("navigator.scheduling.isInputPending: missing");
}
lines.push("Fallback everywhere: setTimeout(fn, 0) / requestAnimationFrame");
console.log(lines.join("\n"));Matches MDN guidance: learn scheduling, prefer Scheduler for new work, keep a universal yield fallback.
isInputPending().setTimeout / Scheduler fallbacks.navigator.scheduling Helps ResponsivenessMany tasks execute on the main thread.
Input events wait in the browser event queue.
Your loop notices pending interaction.
The browser handles input; your tasks resume afterward.
Scheduling object; main method is isInputPending().Scheduler interface for new scheduling work.Navigator.navigator.scheduling is Experimental and not Baseline. Support is limited (commonly Chromium-based browsers for isInputPending()). Always feature-detect and keep a setTimeout / Scheduler fallback.
Useful for learning input-aware yielding. Prefer Scheduler APIs for new production scheduling when available.
Bottom line: Detect navigator.scheduling.isInputPending, prefer scheduler.yield when present, and never require this API for core UX.
navigator.scheduling is an experimental entry point to a Scheduling object whose isInputPending() method helps long scripts stay responsive. Feature-detect it, treat it as optional, and prefer the newer Scheduler API when you can.
Continue with serial, productSub, or the JavaScript hub.
isInputPending()Scheduler APIs for new codesetTimeout(0) fallbacknavigator.schedulingnavigator.schedulingschedulingExperimental entry point — check pending input, prefer Scheduler for new work.
Scheduling
ValueisInputPending
APIexperimental
Cautionread-only
NavigatorScheduler
ModernisInputPending() started as a Facebook contribution to browsers so huge scripts could stay interactive. Today MDN points new work toward the Prioritized Task Scheduling API (Scheduler) instead.
Web Serial API — talk to boards and serial gadgets in the browser.
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