indexedDB函数返回跨模块的导入/导出

Question

我还是一个初学者，所以我希望这是有意义的。

我试图从一个函数与IndexedDB事务/游标导出一个返回变量到另一个模块与get事务，但该请求总是未定义。是否有可能将IndexedDB函数的值跨到同一域中的其他模块?

db.js-函数I am export

...
function getAllData() {
// can use getAll() however not as efficient.
// let data = [];
let data = [];
let store = db.transaction("forms").objectStore("forms");
store.openCursor().onsuccess = (event) => {
let cursor = event.target.result;
if (cursor) {
console.log("FORM name is " + cursor.value.name + " and form counter is " + cursor.key);
// data.push(cursor.value.name);
data.push(cursor.value);
cursor.continue();
} else {
console.log("All entries retrieved");
console.log("the data form.name is " + data);
console.log("the data is " + data.length);
return data.length;
}
}
store.openCursor().onerror = event => {
console.log("Error in getting all data " + event.target.errorCode);
}
};
export { getAllData } ;

a.js

import { getAlldData } from './db.js'
(() => {
function getIndex() {
let formData = getAllData();    
console.log("the counter is " + formData); // shows formData as undefined
}
}
)();

是否可以得到db.js的返回值gettalldata()在a.jsformData吗?console.log在db.js

Answer 1

我看到你让它与回调一起工作。下面是一个使用承诺的例子。

export function getAllData() {
return new Promise((resolve, reject) => {
let data = [];
let store = db.transaction("forms").objectStore("forms");
const request = store.openCursor();
request.onsuccess = (event) => {
let cursor = event.target.result;
if (cursor) {
data.push(cursor.value);
cursor.continue();
} else {
resolve(data);
}
};
request.onerror = event => {
reject(new Error('Error getting all data'));
};
});
}
// and then to use it in another module you do this:
import { getAllData } from 'file';
getAllData().then(data => {
console.log('loaded %d rows', data.length);
for (const row of data) {
console.log('row of data:', JSON.stringify(row));
}
}).catch(error => {
console.log('got an error :( - ', error.message);
});