问题
I'm currently developing a desktop application with Node-webkit. During that process I need to get some data from a local MySQL-database.
The querying works fine, but I can't figure out how to access the results. I store all of them in an array that is then passed to a function. In the console they look like this:
RowDataPacket {user_id: 101, ActionsPerformed: 20}
RowDataPacket {user_id: 102, ActionsPerformed: 110}
RowDataPacket {user_id: 104, ActionsPerformed: 3}
And here is the query structure:
var ret = [];
conn.query(SQLquery, function(err, rows, fields) {
if (err)
alert("...");
else {
for (var i of rows)
ret.push(i);
}
doStuffwithTheResult(ret);
}
How do I retrieve this in the doStuffwithTheResult function? The values are more important, but if I could get the keys as well that would be great.
回答1:
Turns out they are normal objects and you can access them through user_id.
RowDataPacket is actually the name of the constructor function that creates an object, it would look like this new RowDataPacket(user_id, ...). You can check by accessing its name [0].constructor.name
If the result is an array, you would have to use [0].user_id.
回答2:
I also met the same problem recently, when I use waterline in express project for complex queries ,use the SQL statement to query.
this is my solution: first transform the return value(RowDataPacket object) into string, and then convert this string into the json object.
The following is code :
//select all user (查询全部用户)
find: function(req, res, next){
console.log("i am in user find list");
var sql="select * from tb_user";
req.models.tb_user.query(sql,function(err, results) {
console.log('>> results: ', results );
var string=JSON.stringify(results);
console.log('>> string: ', string );
var json = JSON.parse(string);
console.log('>> json: ', json);
console.log('>> user.name: ', json[0].name);
req.list = json;
next();
});
}
The following is console:
>> results: [ RowDataPacket {
user_id: '2fc48bd0-a62c-11e5-9a32-a31e4e4cd6a5',
name: 'wuwanyu',
psw: '123',
school: 'Northeastern university',
major: 'Communication engineering',
points: '10',
datems: '1450514441486',
createdAt: Sat Dec 19 2015 16:42:31 GMT+0800 (中国标准时间),
updatedAt: Sat Dec 19 2015 16:42:31 GMT+0800 (中国标准时间),
ID: 3,
phone: 2147483647 } ]
>> string: [{"user_id":"2fc48bd0-a62c-11e5-9a32-a31e4e4cd6a5","name":"wuwanyu","psw":"123","school":"Northeastern university","major":"Communication engineering","points":"10","datems":"1450514
441486","createdAt":"2015-12-19T08:42:31.000Z","updatedAt":"2015-12-19T08:42:31.000Z","ID":3,"phone":2147483647}]
>> json: [ { user_id: '2fc48bd0-a62c-11e5-9a32-a31e4e4cd6a5',
name: 'wuwanyu',
psw: '123',
school: 'Northeastern university',
major: 'Communication engineering',
points: '10',
datems: '1450514441486',
createdAt: '2015-12-19T08:42:31.000Z',
updatedAt: '2015-12-19T08:42:31.000Z',
ID: 3,
phone: 2147483647 } ]
>> user.name: wuwanyu
回答3:
You can copy all enumerable own properties of an object to a new one by Object.assign(target, ...sources):
trivial_object = Object.assign({}, non_trivial_object);
so in your scenario, it should be enough to change
ret.push(i);
to
ret.push(Object.assign({}, i));
回答4:
With Object.prototype approach, JSON.parse(JSON.stringify(rows)) returns object, extract values with Object.values()
var resultArray = Object.values(JSON.parse(JSON.stringify(rows)))
Usage:
resultArray.forEach(function(v){ console.log(v) })
回答5:
you try the code which gives JSON without rowdatapacket:
var ret = [];
conn.query(SQLquery, function(err, rows, fields) {
if (err)
alert("...");
else {
ret = JSON.stringify(rows);
}
doStuffwithTheResult(ret);
}
回答6:
I found an easy way
Object.prototype.parseSqlResult = function () {
return JSON.parse(JSON.stringify(this[0]))
}
At db layer do the parsing as
let users= await util.knex.raw('select * from user')
return users.parseSqlResult()
This will return elements as normal JSON array.
回答7:
going off of jan's answer of shallow-copying the object, another clean implementation using map function,
High level of what this solution does: iterate through all the rows and copy the rows as valid js objects.
// function will be used on every row returned by the query
const objectifyRawPacket = row => ({...row});
// iterate over all items and convert the raw packet row -> js object
const convertedResponse = results.map(objectifyRawPacket);
We leveraged the array map function: it will go over every item in the array, use the item as input to the function, and insert the output of the function into the array you're assigning.
more specifically on the objectifyRawPacket function: each time it's called its seeing the "{ RawDataPacket }" from the source array. These objects act a lot like normal objects - the "..." (spread) operator copies items from the array after the periods - essentially copying the items into the object it's being called in.
The parens around the spread operator on the function are necessary to implicitly return an object from an arrow function.
回答8:
Simpler way:
.then( resp=> {
let resultFromDb= Object.values(resp)[0]
console.log(resultFromDb)
}
In my example I received an object in response. When I use Object.values I have the value of the property as a response, however it comes inside an array, using [0] access the first index of this array, now i have the value to use it where I need it.
回答9:
I had this problem when trying to consume a value returned from a stored procedure.
console.log(result[0]);
would output "[ RowDataPacket { datetime: '2019-11-15 16:37:05' } ]".
I found that
console.log(results[0][0].datetime);
Gave me the value I wanted.
来源：https://stackoverflow.com/questions/31221980/how-to-access-a-rowdatapacket-object