JavaScript implementation of the timer APIs; `setTimeout`, `clearTimeout`, `setImmediate`, `clearImmediate`, `setInterval`, `clearInterval`, `requestAnimationFrame`, `cancelAnimationFrame`, `requestIdleCallback`, and `cancelIdleCallback`, along with a clock instance that controls the flow of time. FakeTimers also provides a `Date` implementation that gets its time from the clock.
In addition in browser environment `@sinonjs/fake-timers` provides a `performance` implementation that gets its time from the clock. In Node environments FakeTimers provides a `nextTick` implementation that is synchronized with the clock - and a `process.hrtime` shim that works with the clock.
`@sinonjs/fake-timers` is extracted from [Sinon.JS](https://github.com/sinonjs/sinon.js) and targets the [same runtimes](https://sinonjs.org/releases/latest/#supported-runtimes).
Version 7 introduced JSDoc to the codebase. This should provide autocomplete and type suggestions in supporting IDEs. If you need more elaborate type support, TypeScript definitions for the Sinon projects are independently maintained by the Definitely Types community:
the screen. If you want to simulate asynchronous behavior, please see the `async` function variants (eg `clock.tick(time)` vs `await clock.tickAsync(time)`).
The `loopLimit` argument sets the maximum number of timers that will be run when calling `runAll()` before assuming that we have an infinite loop and throwing an error. The default is `1000`.
| `config.now` | Number/Date | 0 | installs FakeTimers with the specified unix epoch |
| `config.toFake` | String[] | ["setTimeout", "clearTimeout", "setImmediate", "clearImmediate","setInterval", "clearInterval", "Date", "requestAnimationFrame", "cancelAnimationFrame", "requestIdleCallback", "cancelIdleCallback", "hrtime", "performance"] | an array with explicit function names (or objects, in the case of "performance") to hijack. _When not set, FakeTimers will automatically fake all methods **except** `nextTick`_ e.g., `FakeTimers.install({ toFake: ["setTimeout","nextTick"]})` will fake only `setTimeout` and `nextTick` |
| `config.loopLimit` | Number | 1000 | the maximum number of timers that will be run when calling runAll() |
| `config.shouldAdvanceTime` | Boolean | false | tells FakeTimers to increment mocked time automatically based on the real system time shift (e.g. the mocked time will be incremented by 20ms for every 20ms change in the real system time) |
| `config.advanceTimeDelta` | Number | 20 | relevant only when using with `shouldAdvanceTime: true`. increment mocked time by `advanceTimeDelta` ms every `advanceTimeDelta` ms change in the real system time. |
| `config.shouldClearNativeTimers` | Boolean | false | tells FakeTimers to clear 'native' (i.e. not fake) timers by delegating to their respective handlers. These are not cleared by default, leading to potentially unexpected behavior if timers existed prior to installing FakeTimers. |
Queued the callback to be fired during idle periods to perform background and low priority work on the main event loop. Callbacks which have a timeout option will be fired no later than time in milliseconds. Returns an `id` which can be used to cancel the callback.
This runs all pending microtasks scheduled with `nextTick` but none of the timers and is mostly useful for libraries using FakeTimers underneath and for running `nextTick` items without any timers.
Implements the `now` method of the [`Performance`](https://developer.mozilla.org/en-US/docs/Web/API/Performance/now) object but using the clock to provide the correct time. Only available in environments that support the Performance object (browsers mostly).
In order to support creating clocks based on separate or sandboxed environments (such as JSDOM), FakeTimers exports a factory method which takes single argument `global`, which it inspects to figure out what to mock and what features to support. When invoking this function with a global, you will get back an object with `timers`, `createClock` and `install` - same as the regular FakeTimers exports only based on the passed in global instead of the global environment.