Created
May 24, 2016 12:10
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function sumf(n) { | |
let sum = 0; | |
for (let i = n; i > 0; i--) { | |
sum += i * (n - i + 1); | |
} | |
return sum; | |
} |
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function transform(...objs) { | |
let obj = Object.assign({}, ...(objs.reverse())); | |
let keys = Object.keys(obj).reverse(); | |
let funcKeys = keys.filter(key => typeof obj[key] === 'function'); | |
let promises = funcKeys.map(key => obj[key]()); | |
return Promise.all(promises) | |
.then(keys => { | |
return Promise.all(keys.map(key => { | |
let value = obj[key]; | |
return funcKeys.includes(key) ? value() : value; | |
})); | |
}) | |
.then(result => result.filter(v => v).join('')); | |
} |
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function letterPromises() { | |
function promise(value, delay) { | |
let promise = new Promise(resolve => setTimeout(() => resolve(value), delay)); | |
return promise.then(value => console.log(value)); | |
} | |
return promise('a', 100) | |
.then(() => Promise.all([promise('b', 100), promise('c', 100), promise('d', 100)])) | |
.then(() => Promise.all([ | |
promise('e', 100).then(() => promise('f', 100)).then(() => promise('h', 100)), | |
promise('g', 200) | |
])) | |
.then(() => promise('i', 100)) | |
.then(() => promise('j', 100)); | |
} |
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