JavaScript 等待多个并发承诺中的第一个
示例
该静态方法接受一个可迭代的承诺，并返回一个新的承诺，它解决或拒绝尽快的第一个在承诺的迭代已经解决或拒绝。Promise.race()
// wait "milliseconds" milliseconds, then resolve with "value"
function resolve(value, milliseconds) {
return new Promise(resolve => setTimeout(() => resolve(value), milliseconds));
}
// wait "milliseconds" milliseconds, then reject with "reason"
function reject(reason, milliseconds) {
return new Promise((_, reject) => setTimeout(() => reject(reason), milliseconds));
}
Promise.race([
resolve(1, 5000),
resolve(2, 3000),
resolve(3, 1000)
])
.then(value => console.log(value)); // outputs "3" after 1 second.
Promise.race([
reject(new Error('坏事！'), 1000),
resolve(2, 2000)
])
.then(value => console.log(value)) //不输出任何东西
.catch(error => console.log(error.message)); // outputs "坏事！" after 1 second