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Basic promise implementation
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| /* Very basic promise implementation */ | |
| class Promise { | |
| observers: []; | |
| value: T; | |
| resolved: Boolean; | |
| constructor(){ | |
| this.observers = []; | |
| this.resolved = false; | |
| this.value = undefined; | |
| } | |
| // onSuccess :: Promise t -> (t -> ()) -> () | |
| onSuccess(cb){ | |
| if( this.resolved ) | |
| cb(this.value) | |
| else | |
| this.observers.push(cb) | |
| } | |
| // resolve :: Promise t -> t -> () | |
| resolve(value){ | |
| this.value = value; | |
| this.resolved = true; | |
| this.observers.forEach(obs => obs(value)) | |
| } | |
| // map :: Promise t -> (t -> u) -> Promise u | |
| map(fn){ | |
| var p = new Promise() | |
| this.onSuccess( result => p.resolve(fn(result))) | |
| return p; | |
| } | |
| // bind :: Promise t -> (t -> Promise u) -> Promise u | |
| bind(fn){ | |
| var p = new Promise() | |
| this.onSuccess( result => fn(result).onSuccess( r => p.resolve(r))) | |
| return p; | |
| } | |
| } | |
| function later(delay, value){ | |
| var p = new Promise(); | |
| setTimeout( () => p.resolve(value), delay) | |
| return p; | |
| } | |
| var p1 = later(100, 5) | |
| .map(x => x * 2) | |
| .map( x => x + "!" ) | |
| var p2 = p1 | |
| .bind( x => later(200, x + ' - more')) | |
| .bind( x => later(300, x + ' !!!')) | |
| p1.onSuccess(r => console.log("a1: ", r)) | |
| p2.onSuccess(r => console.log("a2: ", r)) | |
| setTimeout( () => p1.onSuccess(r => console.log("b1: ", r)), 1000) | |
| setTimeout( () => p2.onSuccess(r => console.log("b2: ", r)), 1000) |
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