javascript - DynamoDB API Node ，是否可以同步获取结果？

Question

我知道正常的做事方式是

db.query(params, callback);

但是我如何以及可以做类似的事情

var data = db.query(params);

如果我的 lambda 的其余部分在我得到结果之前无法执行，它是否可以在没有所有回调的情况下等待它？

Answer 1

Query api 没有同步方式。但是，您可以将 Promise 用于查询 API。

Promises provide an alternative to the use of a callback function to manage asynchronous flow. They allow treating asynchronous calls as a variable, simplifying error handling and providing greater control over handling results from asynchronous calls.

AWS SDK support for promise

使用查询 API 的示例代码:-

var table = "Movies";

var year_val = 1992;
var title = "Movie with list attribute";

var params = {
    TableName: table,
    KeyConditionExpression: 'yearkey = :hkey and title = :rkey',
    ExpressionAttributeValues: {
        ':hkey': year_val,
        ':rkey': title        
    }
};

var queryObjectPromise = docClient.query(params).promise();

queryObjectPromise.then(function (data) {
    console.log("Query Item succeeded: ", JSON.stringify(data,
        null, 2));
}).catch(function (err) {
    console.log("Unable to read item. Error JSON: ", JSON.stringify(err, null, 2));

});