Not same value in the same variable - node.js

Question

I am running into issues putting many items in DynamoDB
I am using this lib : https://github.com/baseprime/dynamodb
I get the error : The conditional request failed
Here is my code
const addInput = input => {
console.log('input', input);
return new Promise((resolve, reject) => {
Input.create(
{
id: input.id,
playlist: input.playlist
},
{
overwrite: false
},
(err, inputRes) => {
if (err) {
console.log('input2', input);
console.log('inputRes', inputRes);
console.log('err', err);
reject(err);
}
resolve(inputRes.get('id'));
}
);
});
};
And my logs shows for the same lambda request id
input { id: 1567787730645,
playlist: 2010}
input2 { id: 1567786871913,
playlist: 80}
inputRes undefined
err { ConditionalCheckFailedException: The conditional request failed ..
How can the input variables have different values ?

Answer 1

Here's the fix:
const addInput = input => {
const data = { id: input.id, playlist: input.playlist };
console.log('input', input);
return new Promise((resolve, reject) => {
Input.create(data,
{
overwrite: false
},
(err, inputRes) => {
if (err) {
console.log('input2', input);
console.log('inputRes', inputRes);
console.log('err', err);
reject(err);
}
resolve(inputRes.get('id'));
});
});
};
Exaplanation
You make the Input.create() inside the Promise's function. This function is not invoked when the promise is created. Instead, it is invoked at some unknown time in the future. This means that after addInput() any changes made to the object passed to addInput() will affect the id, playlist values passed to Input.create(). By copying these values at the beginning of addInput(), and not inside the Promise's function, you fix this problem.