jQuery indexedDB - 如果找到记录，则返回 true

Question

我想编写一个函数，使用 jQuery 插件检查 IndexedDB 中是否存在定义的值。

我尝试使用它，但它不起作用，因为找到的返回是在 promise.done() 完成之前执行的。我该如何解决这个问题？

非常感谢。

function equipmentHasOrder(equipment) {
var orderObjectStore = $.indexedDB("order").objectStore("openOrders");
var found = false;

var index = orderObjectStore.index("EQUIPMENT");
var promise = index.get(equipment);

promise.done(function (result, event) {
    if(result !== undefined) {
        found = true;
    }
});

return found;

promise.fail(function (error, event) {
    error; // Type of error that has occured
    event; // Error event
    event.type; // indicates if there was an error or an exception
});

Answer 1

你可以用then链接承诺：

function equipmentHasOrder(equipment){
    var orderObjectStore = $.indexedDB("order").objectStore("openOrders");

    var index = orderObjectStore.index("EQUIPMENT");
    var promise = index.get(equipment);

    // note the `.then` for chaining and the fact we're returning it.
    return promise.then(function (result) {
        return (result !== undefined);
    });
}

那么你就可以做到：

equipmentHasOrder(equipment).then(function(result){
     if(result){ // found

     } else { // handle not found

     }
});