Create a `Readable` stream that swithes to the fallback on error
npm install fallback-stream
Create a Readable stream that switches to the fallback on error
``javascript
const {createReadStream} = require('fs');
const fallbackStream = require('fallback-stream');
fallbackStream([
createReadStream('foo.txt'), // foo.txt doesn't exist
createReadStream('bar.txt'), // bar.txt: 'Hello!'
createReadStream('baz.txt') // baz.txt doesn't exist
])
.pipe(process.stdout); // yields 'Hello!'
`
`
npm install fallback-stream
`javascript`
const fallbackStream = require('fallback-stream');
array: Array (directly passed to multistream) Object | Function | RegExp
options: stream.Readable
Return:
When the first stream emits an error, the next one starts, and so on until one of the streams ends successfully. In other words, when the one of the streams ended, the rest won't be used.
`javascript
const firstStream = fs.createReadStream('path/to/file/foo');
const fallback = fs.createReadStream('path/to/file/bar');
// a function that returns a readable stream
const fallbackFn = () => fs.createReadStream('path/to/file/baz');
fallbackStream([
firstStream,
fallback,
fallbackFn
]);
`
#### options
It supports stream.Readable options and the following:
##### errorFilter
Type: Function | RegExp function() { return true }
Default:
Filter errors that streams emit. If the filtering result is falsy, the created stream emits an error immediately and won't use the rest of streams.
`javascript
function createErrorStream(err) {
const stream = new stream.PassThrough();
process.nextTick(() => stream.emit('error', err));
return stream;
}
createStreams = function() {
return [
createErrorStream(new TypeError()),
createErrorStream(new RangeError()),
createErrorStream(new SyntaxError())
];
}
fallbackStream(createStreams(), {}).on('error', err => {
err.name; //=> 'SyntaxError'
});
fallbackStream(createStreams(), {
errorFilter(err) {
return err.name === 'RangeError';
}
}).on('error', err => {
err.name; //=> 'TypeError'
});
fallbackStream(createStreams(), {
errorFilter: /TypeError/
}).on('error', err => {
err.name; //=> 'RangeError'
});
`
You can directly pass a Function or RegExp to the second argument to specify the error filter simply, instead of passing an object.
`javascript`
fallbackStream([/ streams /], /ENOENT/);
#### stream.\_errors
Type: Error[] []
Default:
The Error`s that streams were supposed to emit but didn't.
Copyright (c) Shinnosuke Watanabe
Licensed under the MIT License.