Wait for a condition to be true
npm install p-wait-for> Wait for a condition to be true
Can be useful for polling.
``sh`
npm install p-wait-for
`js
import pWaitFor from 'p-wait-for';
import {pathExists} from 'path-exists';
await pWaitFor(() => pathExists('unicorn.png'));
console.log('Yay! The file now exists.');
`
Returns a Promise that resolves when condition returns true. Rejects if condition throws or returns a Promise that rejects.
#### condition
Type: Function
Expected to return Promise or a value from pWaitFor.resolveWith().
#### options
Type: object
##### interval
Type: number\20
Default:
Number of milliseconds to wait after condition resolves to false before calling it again.
##### timeout
Type: number | TimeoutOptions\Infinity
Default:
Number of milliseconds to wait before automatically rejecting with a TimeoutError.
You can customize the timeout Error by specifying TimeoutOptions.
`js
import pWaitFor from 'p-wait-for';
import {pathExists} from 'path-exists';
await pWaitFor(() => pathExists('unicorn.png'), {
timeout: {
milliseconds: 100,
message: new Error('Time’s up!')
}
});
console.log('Yay! The file now exists.');
`
###### milliseconds
Type: number
Milliseconds before timing out.
Passing Infinity will cause it to never time out.
###### message
Type: string | Error
Specify a custom error message or error. If not specified, the default error message will be 'Promise timed out after {milliseconds} milliseconds' where {milliseconds} is replaced with the actual timeout value.
If you do a custom error, it's recommended to sub-class TimeoutError.
###### fallback
Type: Function
Do something other than rejecting with an error on timeout.
You could for example retry with more attempts.
Example:
`js
import pWaitFor from 'p-wait-for';
import {pathExists} from 'path-exists';
const result = await pWaitFor(() => pathExists('unicorn.png'), {
timeout: {
milliseconds: 50,
fallback: () => {
console.log('Time’s up! Executed the fallback function.');
return 'default-value';
},
}
});
console.log(result); // 'default-value'
`
##### before
Type: boolean\true
Default:
Whether to run the check immediately rather than starting by waiting interval milliseconds.
Useful for when the check, if run immediately, would likely return false. In this scenario, set before to false.
##### signal
Type: AbortSignal
An AbortSignal to cancel the wait operation.
Resolve the main promise with a custom value.
`js
import pWaitFor from 'p-wait-for';
import {pathExists} from 'path-exists';
const path = await pWaitFor(async () => {
const path = getPath();
return await pathExists(path) && pWaitFor.resolveWith(path);
});
console.log(path);
``
Exposed for instance checking.
- p-whilst - Calls a function repeatedly while a condition returns true and then resolves the promise
- More…