可以满足需求，且使用方法和Promise.all统一
var a = function() {
return new Promise(function(resolve, reject) {
setTimeout(function() {
console.log('a')
resolve('a')
}, 1000)
})
}
var b = function(data) {
return new Promise(function(resolve, reject) {
console.log('b')
resolve(data +'b')
})
}
var c = function(data) {
return new Promise(function(resolve, reject) {
setTimeout(function() {
console.log('c')
resolve(data +'c')
}, 500)
})
}
// 组织函数队列
function reduce(arr) {
var sequence = Promise.resolve()
arr.forEach(function(item) {
sequence = sequence.then(item)
})
return sequence
}
// 顺序执行函数队列
reduce([a, b, c])
.then(function(data) {
console.log(data)// abc
})
.catch(function(e) {
console.log(e)
})