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我想获取多个JSON文件。这是我的代码:
var timestamps = [];
var urls = ['assets/layouts/default.json','assets/layouts/simple.json'];
var jsons = [];
Promise.all(urls.map(url => {
fetch(url)
.then(data => data.json())
.then(json => {
jsons.push(json);
timestamps.push(performance.now());
});
}))
.then(() => {
console.log(`All assets loaded. Assets were loaded at: ${timestamps}, this log was made at ${performance.now()}. Loaded data: ${jsons}`);
}
);
问题是 Promise.all 似乎过早解决了。如您所见，我进行了一些调试，它记录了以下内容:
All assets loaded. Assets were loaded at: , this log was made at 37.73. Loaded data:
如果我将 console.log 包装在 setTimeout 中，并在 Promise.all 解析时保存时间，如下所示:
.then(() => {
let promiseResolvedAt = performance.now();
setTimeout(() => {
console.log(`All assets loaded. Assets were loaded at: ${timestamps}, Promise.all was resolved at ${promiseResolvedAt}. Loaded data: ${jsons}`);
})
}
我明白了:
All assets loaded. Assets were loaded at: 63.44000000000001,63.555, Promise.all was resolved at 55.96500000000001. Loaded data: [object Object],[object Object]
我可以通过使用 setTimeout 让它按照我想要的方式工作，但我确信有更好的方法，我只是在这里做错了。
为什么 Promise.all 在它的组件 promise 解析之前解析？
我在 Chrome 55 上运行它。