Node.js 如何利用異步提升任務(wù)處理速度

async fetchSceneTags(imagePath) {
 try {
 const result = await callAliyunAPI(imagePath);
 return result.errno === 0 ? result.tags : [];
 } catch(error) {
 return []; 
 }
}

async function writeScene(paths) {
 for (let i = 0, len = paths.length; i < len; i++) {
 await tags = fetchSceneTags(paths[i])
 writeToFile(tags);
 writeStdout(`${i} / ${len}`);
 }
}

function start() {
 const paths = loadPaths();
 writeScene(paths);
}

fetchSceneTagsAsync(imagePath, callback) {
 callAliyunAPI(imagePath)
 .then(result => {
 const tags = result.errno === 0 ? result.tags : [];
 callback(tags);
 })
 .catch(error => callback([]));
}

function writeSceneAsync(paths) {
 const callback = tags => {
 await tags = fetchSceneTagsAsync(paths[i])
 writeToFile(tags);
 }
 
 paths.forEach(path => fetchSceneTagsAsync(path, callback));
}

function start() {
 const paths = loadPaths();
 writeSceneAsync(paths);
}

fetchSceneTagsAsync(imagePath, callback) {
 callAliyunAPI(imagePath)
 .then(result => {
 const tags = result.errno === 0 ? result.tags : [];
 callback(tags);
 })
 .catch(error => callback([]));
}

function throttle(paths, callback) {
 if(paths.length === 0) return;
 
 const sub = paths.splice(0, 10);
 sub.forEach(path => fetchSceneTagsAsync(path, callback));
 setTimeout(() => throttle(paths, callback), 1000)
}

function writeSceneAsync(paths) {
 const callback = tags => {
 await tags = fetchSceneTagsAsync(paths[i])
 writeToFile(tags);
 }
 
 throttle(paths, callback)
}

function start() {
 const paths = loadPaths();
 writeSceneAsync(paths);
}