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class Callback { | |
constructor(f) { | |
// this.run = f | |
this.run = callback => { | |
try { | |
f(callback) | |
} catch (ex) { | |
callback(ex, null) | |
} | |
} | |
// this :: Callback x | |
// (x -> y) -> Callback y | |
this.map = g => new Callback(callback => { | |
this.run((error, ...result) => { | |
if(!!error) { | |
callback(error, null) | |
} else { | |
callback(null, g(...result)) | |
} | |
}) | |
}) | |
// this :: Callback x | |
// (x -> Callback y) -> Callback y | |
this.bind = g => new Callback(callback => { | |
this.run((error, ...result) => { | |
if(!!error) { | |
callback(error, null) | |
} else { | |
g(...result).run(callback) | |
} | |
}) | |
}) | |
// this :: Callback x | |
// x -> (y || Callback y) -> Callback y | |
this.then = g => new Callback(callback => { | |
this.run((error, ...result) => { | |
if(!!error) { | |
callback(error, null) | |
} else { | |
try { | |
const y = g(...result) | |
if (y instanceof Callback) { | |
y.run(callback) | |
} else { | |
callback(null, y) | |
} | |
} catch(ex) { | |
callback(ex, null) | |
} | |
} | |
}) | |
}) | |
this.bindTo = g => this.bind(Callback.from(g)) | |
} | |
} | |
// x -> Callback x | |
Callback.pure = x => new Callback(cb => cb(null, x)) | |
Callback.resolve = Callback.pure | |
// Callback.from casts f into a Callback instance, where | |
// f is a function that takes x and a callback function | |
Callback.from = f => (...x) => new Callback(cb => f(...x, cb)) |
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Usage: https://jsbin.com/jazadi/edit?js,console