Node.js can';t将映射设置为异步
我正在尝试从s3中读取一个文件,该文件存储了艺术家的名字,并在youtube上获得了前10首歌曲。Node.js can';t将映射设置为异步,node.js,amazon-s3,youtube-api,Node.js,Amazon S3,Youtube Api,我正在尝试从s3中读取一个文件,该文件存储了艺术家的名字,并在youtube上获得了前10首歌曲。 我能够获取s3数据,并且能够使用youtube数据api获取数据, 我想将数据存储在我创建的名为singer的对象数组中 console.log("Loading up the best code ever!!!"); var fs = require('fs'); // Load the SDK for JavaScript var AWS = require('aws-sdk'); var
我能够获取s3数据,并且能够使用youtube数据api获取数据,
我想将数据存储在我创建的名为singer的对象数组中
console.log("Loading up the best code ever!!!");
var fs = require('fs');
// Load the SDK for JavaScript
var AWS = require('aws-sdk');
var jsonfile = require('jsonfile')
var Singer = require('./Singer')
// Set the region
AWS.config.update({ region: "us-west-1" });
var credentials = new AWS.SharedIniFileCredentials();
AWS.config.credentials = credentials;
// Create S3 service object
s3 = new AWS.S3({ apiVersion: '2006-03-01' });
console.log("after S3");
// Create the parameters for calling createBucket
var bucketParams = {
Bucket: 'pc-backend-exercises',
Key: 'toSearch.json',
ResponseContentType: 'application/json'
};
/// youtube part
var YTAPI = require('node-youtubeapi-simplifier');
var APIKEY = 'kekekek'
YTAPI.setup(APIKEY);
var singers = [];
var print = function printJson() {
console.log('entered printJson')
console.log(singers);
var results = {}
for (var i = 0; i < singers.length; i++) {
results[singers[i].name] = singers[i];
}
JSON.stringify(results);
console.log(results);
}
s3.getObject(bucketParams, function (err, data) {
// Handle any error and exit
console.log('download json file from s3');
if (err) {
console.log(err, err.stack);
return err;
}
var fileContents = data.Body.toString();
var json = JSON.parse(fileContents);
for (var i = 0; i < json.Search.artists.length; i++) {
var newSinger = new Singer(json.Search.artists[i]);
singers.push(newSinger);
}
search10TopForASinger(print);
});
function search10TopForASinger(print) {
console.log('entered search10TopForASinger ')
for (var i = 0; i < singers.length; i++) {
//Gets only 10 results
var songsMap = singers[i].songs;
YTAPI.searchFunctions.simpleSearch(singers[i].name).then(
function (data) {
setMap(data,songsMap);
});
}
print();
}
function setMap(data, songs) {
console.log('entered setMap')
var size = 10;
if (data.length < 10) {
size = data.length;
}
for (var i = 0; i < size; i++) {
songs.set(i, data[i].title);
}
console.log(songs);
}
因此,代码正在运行,我确实找到了每个歌手的前10首歌曲,但是当我转到printJson函数时,歌曲映射为空请记住,同步代码不会等待异步代码解析。它将触发异步函数,然后立即转到下一行。所以在这个函数中:
function search10TopForASinger(print) {
console.log('entered search10TopForASinger ')
for (var i = 0; i < singers.length; i++) {
//Gets only 10 results
var songsMap = singers[i].songs;
YTAPI.searchFunctions.simpleSearch(singers[i].name).then(
function (data) {
setMap(data,songsMap);
});
}
print();
}
Promise.all
接受一系列承诺,这就是歌手的承诺。map将返回。它将返回一个promise本身,该promise本身只在数组中的每个promise完成后才解析
如果您正在运行Node 8,还可以使用,无需进行太多重构:
async function search10TopForASinger(print) {
for (var i = 0; i < singers.length; i++) {
var songsMap = singers[i].songs;
var data = await YTAPI.searchFunctions.simpleSearch(singers[i].name);
setMap(data, songsMap);
}
print();
}
异步函数search10TopForASinger(打印){
对于(变量i=0;i
这基本上会创建一个
。然后在后台创建一个链,因此函数的每一部分都将等待wait
解析后继续。请记住,您必须将search10TopForASinger
转换为一个异步函数,才能使其正常工作。我会添加一些控制台日志并检查您的假设。我很好奇当第65行实际被调用时,signers
和I
等于什么,因为根据您的日志判断,singers[I]
是未定义的。@ZacDelventhal我已经更新了我的代码,地图在那里,但我无法更新它以将其放到outterscope上
function search10TopForASinger(print) {
Promise.all(singers.map(function(singer) {
var songsMap = singer.songs;
return YTAPI
.searchFunctions
.simpleSearch(singer.name)
.then(function(data) {
setMap(data, songsMap)
})
})).then(function(results) {
print()
})
}
async function search10TopForASinger(print) {
for (var i = 0; i < singers.length; i++) {
var songsMap = singers[i].songs;
var data = await YTAPI.searchFunctions.simpleSearch(singers[i].name);
setMap(data, songsMap);
}
print();
}