41.说说Promise自身的静态方法

41.说说Promise自身的静态方法

1. Promise.all （有一个失败就失败，所有的都成功就成功）
2. Promise.race （有一个成功就成功，有一个失败就失败）
3. Promise.allSettled （所有的异步操作执行完毕之后，才返回）
4. Promise.any （只要有一个成功就成功，所有的都失败，才失败）
5. Promise.resolve （返回一个成功状态的promise对象）
6. Promise.reject (返回一个失败状态的promise对象)

验证

Promise.all 一个失败及失败，都成功则成功

/* 1. Promise.all  一个失败及失败，都成功则成功 */
var a1 = Promise.resolve(1)
var a2 = Promise.resolve(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)


console.log(Promise.all([a1, a2, a3, a4]))
// [1,2,3,4]

var a1 = Promise.resolve(1)
var a2 = Promise.reject(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)

console.log(Promise.all([a1, a2, a3, a4]))
// 报错 返回 2

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2. Promise.race 一个状态变化，就立刻返回

/* 2. Promise.race 一个状态变化，就立刻返回*/
var a1 = Promise.resolve(1)
var a2 = Promise.resolve(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.race([a1, a2, a3, a4]))
// 1

var a1 = Promise.reject(2)
var a2 = Promise.reject(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.race([a1, a2, a3, a4]))
// 2

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3. Promise.allSettled 状态都变化完毕后，再返回

/* 3. Promise.allSettled 状态都变化完毕后，再返回 */
var a1 = Promise.resolve(1)
var a2 = Promise.resolve(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.allSettled([a1, a2, a3, a4]))
// [1,2,3,4]

var a1 = Promise.resolve(1)
var a2 = Promise.reject(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.allSettled([a1, a2, a3, a4]))
// [1,2,3,4]  // 其中reject的状态为失败，其他的状态为成功
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4. Promise.any 一个成功及成功，都失败则失败，和all相反

/* 4. Promise.any 一个成功及成功，都失败则失败，和all相反 */
var a1 = Promise.resolve(1)
var a2 = Promise.resolve(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.any([a1, a2, a3, a4]))
// 1

var a1 = Promise.reject(1)
var a2 = Promise.reject(2)
var a3 = Promise.resolve(3)
var a4 = Promise.resolve(4)
console.log(Promise.any([a1, a2, a3, a4]))
// 2  

var a1 = Promise.reject(1)
var a2 = Promise.reject(2)
var a3 = Promise.reject(3)
var a4 = Promise.reject(4)
console.log(Promise.any([a1, a2, a3, a4]))
// 失败状态 AggregateError: All promises were rejected

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