How to scan in dynamoDB based on the values in an array? - node.js

Question

here is my code where i have a list of values in an array. I need to fetch all the projects from project table which matches the id's in the array.
var arr=[];
for(var index in data.Items){
if(data.Items[index].hasOwnProperty('projectId'))
arr.push(data.Items[index].projectId);
};
var params = {
TableName: 'projects',
FilterExpression: 'id IN (:id)',
ExpressionAttributeValues: {
':id': arr
}
};
dynamodbclient.scan(params, function (err, docs) {
if (err) {
console.log("Error", err);
} else {
console.log("Success");
callback(err, docs.Items);
}
});
However i am not getting the proper results.

Answer 1

Option 1 - Static :-
If you know all the values its count upfront, please construct the FilterExpression as mentioned below:-
var params = {
TableName : "projects",
FilterExpression : "id IN (:id1, :id2)",
ExpressionAttributeValues : {
":id1" : "id val 1",
":id2" : "id val 2"
}
};
Option 2 - Dynamic:-
var titleValues = ["The Big New Movie 2012", "The Big New Movie"];
var titleObject = {};
var index = 0;
titleValues.forEach(function(value) {
index++;
var titleKey = ":titlevalue"+index;
titleObject[titleKey.toString()] = value;
});
var params = {
TableName : "Movies",
FilterExpression : "title IN ("+Object.keys(titleObject).toString()+ ")",
ExpressionAttributeValues : titleObject
};
docClient.scan(params, onScan);
function onScan(err, data) {
if (err) {
console.error("Unable to scan the table. Error JSON:", JSON.stringify(
err, null, 2));
} else {
// print all the movies
console.log("Scan succeeded.");
data.Items.forEach(function(movie) {
console.log("Item :", JSON.stringify(movie));
});
// continue scanning if we have more movies
if (typeof data.LastEvaluatedKey != "undefined") {
console.log("Scanning for more...");
params.ExclusiveStartKey = data.LastEvaluatedKey;
docClient.scan(params, onScan);
}
}
}