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自作promiseそれなりには動くはず
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function promise(fn){ | |
var self = { | |
status: "pending", | |
value: undefined, | |
nexts: [], | |
__proto__: promise.prototype | |
} | |
function common(value, status){ | |
if(self.status !== "pending") return | |
self.status = status | |
self.value = value | |
self.doNexts() | |
} | |
var resolve = value => common(value, "resolved") | |
var reject = value => common(value, "rejected") | |
try{ | |
fn(resolve, reject) | |
}catch(e){ | |
reject(e) | |
} | |
return self | |
} | |
promise.prototype.then = function(fn){ | |
return this._common(fn, "resolved") | |
} | |
promise.prototype.catch = function(fn){ | |
return this._common(fn, "rejected") | |
} | |
promise.prototype._common = function(fn, status){ | |
return promise((aa,bb) => { | |
var f = (value) => { | |
if(this.status === status){ | |
try{ | |
var result = fn(value) | |
}catch(e){ | |
return bb(e) | |
} | |
if(result && result instanceof promise){ | |
result.then(e => aa(e)) | |
result.catch(e => bb(e)) | |
}else{ | |
aa(result) | |
} | |
}else{ | |
this.status === "resolved" ? aa(value) : bb(value) | |
} | |
} | |
if(this.status === "pending"){ | |
this.nexts.push(f) | |
}else{ | |
f(this.value) | |
} | |
}) | |
} | |
promise.prototype.doNexts = function(){ | |
while(this.nexts.length) this.nexts.shift()(this.value) | |
} | |
promise.resolve = () => ({ | |
status: "resolved", | |
value: undefined, | |
nexts: [], | |
__proto__: promise.prototype | |
}) | |
promise.reject = () => ({ | |
status: "rejected", | |
value: undefined, | |
nexts: [], | |
__proto__: promise.prototype | |
}) |
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var p = promise((a,b) => setTimeout(a, 1000, 12)) | |
p.then(e => console.log(e)) | |
p.then(e => console.log(e+1)) | |
p.then(e => console.log(e+2)) | |
// 12 | |
// 13 | |
// 14 | |
var p = promise((a,b) => setTimeout(a, 1000, 16)) | |
p.then(e => e / 4).then(e => e + 2).then(e => console.log(e * e)) | |
// 36 | |
var p = promise((a,b) => setTimeout(b, 1000, 16)) | |
p.then(e => console.log(e)).catch(e => console.log(-e)) | |
// -16 | |
promise((a,b) => setTimeout(a, 1000, 1)) | |
.then(e => promise((a,b) => setTimeout(a, 1000, e+1))) | |
.then(e => console.log(e)) | |
// 2 | |
promise((a,b) => a()) | |
.then(e => promise.reject()) | |
.catch(e => console.log(111)) | |
// 111 | |
promise((a,b) => a(1)).then(e => no_defined_value).catch(e => console.log(e)) | |
// ReferenceError: no_defined_value is not defined(…) | |
promise((a,b) => no_defined_value).then(e => 1).catch(e => console.log(e)) | |
// ReferenceError: no_defined_value is not defined(…) | |
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