DynamoDb Update an Item from Node.js - amazon-dynamodb

Question

I had the following code which originally worked for creating a user.
var params = {
TableName: 'myproject-user',
Item: {
id: req.body.userName,
email: req.body.email
}
};
if(req.body.currency) {
params.Item.currency = {
type: req.body.currency.type,
bank: req.body.currency.bank,
amount: req.body.currency.amount,
}
}
docClient.put(params, function(err, data) {
if (err) {
res.send({
success: false,
message: 'Error: ' + err
});
} else {
const { Items } = data;
res.send({
success: true,
message: 'Added user',
email: req.body.email
});
}
});
I'm now switching to put to update, as I want to be able to keep any existing values on the object while updating the email or name. In addition I have added the following line in the params object to specify the key which is id.
Key: { id : req.user.sub },
The doc.update code executes and I get back status 200 as if there was no problem, but when I look at the table the information hasn't been updated.
Do I need to use an expression or something to get update to work?
Code with changes:
var params = {
TableName: 'myproject-user',
Key: {"id":req.user.sub},
Item: {
id: req.body.userName,
email: req.body.email
}
};
docClient.update(params, function(err, data) {
if (err) {
res.send({
success: false,
message: 'Error: ' + err
});
} else {
const { Items } = data;
res.send({
success: true,
message: 'Added user',
email: req.body.email
});
}
});

Answer 1

I was able to get this working by using UpdateExpression, ExpressionAttributeValues, and ReturnValues attributes instead of Item, as described here:
var params = {
TableName: 'krncdev-user',
Key: {"id":req.user.sub},
UpdateExpression: "set email=:e",
ExpressionAttributeValues:{
":e": req.body.email
},
ReturnValues:"UPDATED_NEW"
};