bluebird

http://bluebirdjs.com/docs/getting-started.html
https://github.com/petkaantonov/bluebird

https://developer.ibm.com/zh/articles/wa-lo-use-bluebird-implements-power-promise/

https://www.bootcdn.cn/bluebird/

bluebird是一个第三方Promise类库，相比其它第三方类库或标准对象来说，功能更齐全而不臃肿、浏览器兼容性更好。

我们可通过npm命令来安装：npm install bluebird

通过require获取对模块的引用：cnst Promise = require(‘bluebird’);

var Promise = require(“bluebird”);
var fs = require(“fs”);
//方法Promise化
var readFileAsync = Promise.promisify(fs.readFile);

//.spread([Function fulfilledHandler] [, Function rejectedHandler ]) -> Promise
//用法:将结果集拆分
//example
Promise.delay(0).then(function () {
return [
readFileAsync(‘1.txt’, ‘utf-8’),
readFileAsync(‘2.txt’, ‘utf-8’),
readFileAsync(‘3.txt’, ‘utf-8’)
];
}).spread(function (file1, file2, file3) {
console.log(file1);
console.log(file2);
console.log(file3);
})

//.finally(Function handler) -> Promise
//类似try..catch..finally中finally的作用
//example
Promise.delay(0).then(function () {
return [
readFileAsync(‘1.txt’, ‘utf-8’),
readFileAsync(‘2.txt’, ‘utf-8’),
readFileAsync(‘4.txt’, ‘utf-8’)
];
}).spread(function (file1, file2, file3) {
console.log(file1);
console.log(file2);
console.log(file3);
}).catch(function (e) {
console.log(e);
}).finally(function () {
//抛错最后仍执行finally中的内容；
console.log(4)
})

//Promise.join(Promise|Thenable|value promises…, Function handler) -> Promise
//将几个promise化的函数join起来，用法有点类似spread
//example
var join = Promise.join;
join(readFileAsync(‘1.txt’, ‘utf-8’),
readFileAsync(‘2.txt’, ‘utf-8’),
readFileAsync(‘3.txt’, ‘utf-8’), function (file1, file2, file3) {
return parseInt(file1) + parseInt(file2) + parseInt(file3);
}).then(function (content) {
console.log(“SUM结果:” + content);
})

//Synchronous inspection 同步检测
//example
var rf1 = readFileAsync(‘1.txt’, ‘utf-8’);
var rf2 = readFileAsync(‘2.txt’, ‘utf-8’);
var rf3 = readFileAsync(‘3.txt’, ‘utf-8’);
var join = Promise.join;
join(rf1, rf2, rf3, function (file1, file2, file3) {
return parseInt(file1) + parseInt(file2) + parseInt(file3);
}).then(function (content) {
console.log(“SUM结果:” + content);
}).finally(function () {
//.isFulfilled() -> boolean
//检测是否完成
console.log(“success:” + rf1.isFulfilled());
//.isRejected() -> boolean
//检测是否失败
console.log(“fail:” + rf1.isRejected());
//.isPending() -> boolean
//检测是否进行中
console.log(“Pending:” + rf1.isRejected());
//.value() -> dynamic
//成功的结果,一般使用时先判定是否完成
if (rf1.isFulfilled()) {
console.log(rf1.value());
}
//.reason() -> dynamic
//失败原因，同样使用时先判定是否失败
if (rf1.isRejected()) {
console.log(rf1.reason());
}
})

//.all() -> Promise
//参数为数组，并且里面的已promise化，全部成功返回的也为数组
//example
var rfAll1 = readFileAsync(‘1.txt’, ‘utf-8’);
var rfAll2 = readFileAsync(‘2.txt’, ‘utf-8’);
var rfAll3 = readFileAsync(‘3.txt’, ‘utf-8’);
var files = [rfAll1, rfAll2, rfAll3];
Promise.all(files).then(function (s) { console.log(“all:” + s) });

//.props() -> Promise
//类似于.all(),不过参数为object，全部成功返回值也为object
//example
Promise.props({
rfProp1: readFileAsync(‘1.txt’, ‘utf-8’),
rfProp2: readFileAsync(‘2.txt’, ‘utf-8’),
rfProp3: readFileAsync(‘3.txt’, ‘utf-8’)
}).then(function(content){
console.log(JSON.stringify(content));
})

//.settle() -> Promise
//基本等同于.all();
//example
var rfsettle1 = readFileAsync(‘1.txt’, ‘utf-8’);
var rfsettle2 = readFileAsync(‘2.txt’, ‘utf-8’);
var rfsettle3 = readFileAsync(‘3.txt’, ‘utf-8’);
var files = [rfsettle1, rfsettle2, rfsettle3];
Promise.all(files).then(function (s) { console.log(“settle:” + s) });

//.some(int count) -> Promise
//第一个参数为数组，第二个为个数,指的返回值最先返回成功的值
//example
var rfsome1 = readFileAsync(‘1.txt’, ‘utf-8’);
var rfsome2 = readFileAsync(‘2.txt’, ‘utf-8’);
var rfsome3 = readFileAsync(‘3.txt’, ‘utf-8’);
var files = [rfsome1, rfsome2, rfsome3];
Promise.some(files,2).spread(function(first,second){
console.log(“some:” + first);
console.log(“some:” + second);
})

//.map(Function mapper [, Object options]) -> Promise
//参数为数组,不需要promise化，只要map里面的函数promise化就行。 有点类似于数组的map方法
//example
var files = [‘1.txt’,’2.txt’,’3.txt’];
Promise.map(files,function(file){
return readFileAsync(file,’utf-8’);
}).then(function(content){
console.log(“map:” + content) ;
})

//.reduce(Function reducer [, dynamic initialValue]) -> Promise
//概念有点像数组的reduce方法. total为返回的组装值，fileName为item,0为初始值
//example
Promise.reduce([“1.txt”, “2.txt”, “3.txt”], function(total, fileName) {
return readFileAsync(fileName, “utf8”).then(function(contents) {
return total + parseInt(contents, 10);
});
}, 0).then(function(total) {
console.log(“reduce:” + total)
});