By the end of this tutorial, you’ll use Lodash’s _.noop as a safe empty function for defaults, iteratees, and optional callbacks.
Pass _.noop by reference.
Always undefined.
Skip null checks.
Use with _.times.
Empty vs pass-through.
_.noop() ≠ _.noop.
_.noop()?_.noop is Lodash’s built-in no-operation function: call it with any arguments and it returns undefined without side effects. It is not a factory like _.constant()—the utility is the function.
Write _.times(2, _.noop), not _.times(2, _.noop()). Parentheses invoke noop immediately; you pass undefined instead of a function. Same for default params: callback = _.noop, not callback = _.noop().
Reach for _.noop when an API expects a function but you have nothing to run—optional hooks, placeholder handlers, or loops where you only care about iteration count.
Lodash exposes a single shared empty function:
_.noop([...args])_.noop — the function reference—what you pass to other APIs._.noop() — runs once, returns undefined—rarely what you want as a callback slot.undefined, regardless of arguments.import noop from "lodash/noop";
noop(1, 2, 3);
// undefined
_.times(2, _.noop);
// [undefined, undefined]| Task | Code pattern | Notes |
|---|---|---|
| Iterate N times | _.times(n, _.noop) | Side-effect loop |
| Default callback | fn(cb = _.noop) | No if-check |
| Safe invoke | (cb || _.noop)(data) | Optional hook |
| Event stub | el.addEventListener("x", _.noop) | No-op handler |
| Wrong pattern | process(_.noop()) | Passes undefined |
| Native alt | () => {} | New fn each time |
undefinedAlways
_.noopReference
identityReturns input
UtilFunction
_.noop accepts any arguments and ignores them all.
...args OptionalAny values passed when noop is invoked. They are discarded—noop never reads them.
_.noop("a", 1, {})return undefinedThe function always returns undefined, even when called with no arguments.
_.noop() === undefinedreference Typical usagePass _.noop itself to methods expecting a function—not the result of calling it.
_.forEach(arr, _.noop)this IgnoredLike most Lodash utilities used as callbacks, noop does not rely on a specific this binding.
arr.forEach(_.noop)Need a function that returns a fixed value? Use _.constant(). Need to pass inputs through? Use _.identity().
Practical _.noop patterns with copy-ready code, sample output, and interactive Try It Yourself labs.
Official iteratee usage and safe default callbacks.
_.timesThe Lodash docs pattern: run a loop without transforming values.
const result = _.times(3, _.noop);
console.log(result);
// [undefined, undefined, undefined]_.times calls the iteratee once per index. _.noop runs but returns nothing useful—handy when you only need iteration count elsewhere.
Use _.noop as the default parameter—correct pattern from the old tutorial fix.
function process(callback = _.noop) {
console.log("Processing...");
callback("done");
}
process();
process((msg) => console.log("Custom:", msg));
// Processing...
// Processing...
// Custom: doneWhen no callback is passed, callback is _.noop—a callable function. Calling callback() is always safe. Using _.noop() as the default would set callback to undefined and crash.
API hooks, comparisons, and event stubs.
Fetch-style helper with an optional listener that defaults to noop.
function fetchData(onSuccess = _.noop) {
const data = { id: 1, name: "Ada" };
onSuccess(data);
return data;
}
fetchData();
fetchData((user) => console.log(user.name));
// (silent first call)
// AdaYou can always invoke the hook—no if (onSuccess) guard. Callers who do not care pass nothing; callers who care pass a real function.
Three Lodash utilities that look similar but behave differently.
console.log(_.noop("hello"));
console.log(_.identity("hello"));
console.log(_.constant("hello")("ignored"));
// undefined
// "hello"
// "hello"noop discards input. identity returns it. constant ignores input and returns a preset value.
Event placeholders and common mistakes.
Register a handler that intentionally does nothing—use the function reference.
// API requires a handler; real logic added later
const handlers = {
onReady: _.noop,
onError: _.noop,
};
handlers.onReady();
// undefined — safe no-op until you replace the handlerSwap handlers.onReady for a real function when ready. Starting with _.noop keeps objects valid without null checks.
_.noop() as callbackWhy the old tutorial’s process(_.noop()) pattern breaks.
function process(callback) {
callback();
}
// WRONG — _.noop() runs now, returns undefined
// process(_.noop()); // TypeError: callback is not a function
// RIGHT — pass the function itself
process(_.noop);
// runs fine, callback returns undefinedParentheses mean “call now.” For callback slots, pass the function reference unless you intentionally want to invoke it immediately.
_.noop WorksLodash defines one empty function and attaches it as _.noop.
You supply _.noop wherever a function is required—defaults, iteratees, handlers.
The caller runs noop with any arguments; the body is empty.
No side effects, no thrown errors—safe placeholder behavior.
_.noop (reference), not _.noop(), for callback and iteratee slots.callback = _.noop—not callback = _.noop()._.times(2, _.noop) produces [undefined, undefined]._.noop is a function object—_.isFunction(_.noop) is true._.noop is a tiny utility with a clear job: stand in when a function is required but no work is needed. Use it for optional callbacks, harmless iteratees, and stub handlers.
Remember the parentheses trap—pass the reference, invoke it only when you deliberately want to run an empty function right now.
callback = _.noop for optional hooks_.noop to _.times, _.forEach, etc._.noop over creating many () => {} copiesprocess(_.noop())—you pass undefinedcallback = _.noop() as a default parameter_.noopUse these points when you need a harmless empty function.
Pass _.noop.
BasicsAlways returns.
MechanicsOptional callbacks.
PracticalWith _.times.
LodashIn callback slots.
PitfallThe name “noop” comes from computing jargon meaning no operation—a CPU instruction or function that intentionally does nothing, used as a harmless placeholder in pipelines and APIs.
Run the official _.times pattern and try safe optional callbacks.
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