从函数返回数据 [英] Return data from function
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问题描述
如何从reader.onload函数返回数据(csvData).我希望数据将从readCsv函数返回:
How can I return the data (csvData) from the reader.onload function. I want that the data will return from readCsv function:
async readCSV(event) {
const reader = new FileReader();
reader.readAsText(event.target.files[0]);
var csvToJson;
csvToJson = reader.onload = async () => {
const text = reader.result;
const csvData = await this.csvJSON(text);
return csvData;
};
return csvToJson;
}
推荐答案
我看到您已经在使用 async
语法.异步语法会自动将所有内容包装到 Promise 实例
I see that you already using async
syntax. Async syntax automatically wraps everything to Promise instance.
但是您还可以返回承诺手动实例.它使用 resolve
&接受回调拒绝
参数.您可以调用 resolve
来解决承诺.
But you also can return Promise instance manually. It accepts callback with resolve
& reject
arguments. And you can call resolve
to resolve the promise.
async function readCSV(event) {
return new Promise(resolve => {
const reader = new FileReader();
reader.readAsText(event.target.files[0]);
reader.onload = async () => {
const text = reader.result;
const csvData = await this.csvJSON(text);
resolve(csvData);
};
});
}
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