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# inflight
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Add callbacks to requests in flight to avoid async duplication
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## USAGE
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```javascript
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var inflight = require('inflight')
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// some request that does some stuff
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function req(key, callback) {
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// key is any random string. like a url or filename or whatever.
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//
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// will return either a falsey value, indicating that the
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// request for this key is already in flight, or a new callback
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// which when called will call all callbacks passed to inflightk
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// with the same key
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callback = inflight(key, callback)
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// If we got a falsey value back, then there's already a req going
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if (!callback) return
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// this is where you'd fetch the url or whatever
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// callback is also once()-ified, so it can safely be assigned
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// to multiple events etc. First call wins.
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setTimeout(function() {
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callback(null, key)
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}, 100)
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}
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// only assigns a single setTimeout
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// when it dings, all cbs get called
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req('foo', cb1)
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req('foo', cb2)
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req('foo', cb3)
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req('foo', cb4)
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```
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