手写Promise.all和Promise.race
Posted 煜成'Studio
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手写Promise.all和Promise.race
Promise.all
function promiseAll (promises) {
if (!Array.isArray(promises)) {
throw new Error ("promises must to be an array!!!");
}
return new Promise (function (resolve, reject) {
let promiseNum = promises.length;
let resolvedCount = 0;
let resolveValues = new Array(promiseNum);
try {
for (let i = 0; i < promiseNum; i++) {
promises[i].then(function (value) {
resolveValues[i] = value;
if (++resolvedCount === promiseNum) {
resolve(resolveValues);
}
})
} catch (error) {
reject(error);
}
})
}
Promise.race
function promiseRace(promise) {
if (!Array.isArray (promises)) {
throw new Error ("promises must be an array!!!");
}
let resolved = false;
return new Promise(function (resolve, reject) {
try{
promises.forEach(p =>
p.then(data => {
if (!resolved) {
resolved = true;
resolve (data);
}
})
)
} catch (error) {
reject(error);
}
})
}
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手写promise，promise.all，promise.race