Develop Reference

Put items in DynamoDB without knowing the attributes

This feels like a really stupid question, but my lack of JS knowledge combined with lack of AWS knowledge has me in a tight spot! I'm just trying to get to grips with a basic AWS stack i.e. Lambda/Dynamo/API Gateway for some basic API work.
If I want a simple API endpoint to handle PUT requests e.g. https://my.endpoint.amazonaws.com/users. If I have a DynamoDB table with a composite primary key of userID and timestamp I could use the code snippet below to take the unknown data (attributes that weren't known when setting a schema), but this obviously doesn't work well
const dynamo = new AWS.DynamoDB.DocumentClient();
let requestJSON = JSON.parse(event.body);
await dynamo
.put({
TableName: "myDynamoTable",
Item: {
userID: requestJSON.userID,
timestamp: requestJSON.timestamp,
data: requestJSON.data
}
})
.promise();
I could send a PUT request with the following JSON
{
"userID": "aaaa1111",
"timestamp": 1649677057,
"data": {
"address": "Elm Street",
"name": "Glen"
}
}
but then address and name get shoved into a single DynamoDB attribute named data. How do I construct the node code to create a new attribute named address and one named name with the corresponding values, if I didn't know these attributes i.e. I want to use JSON in my request like below, but assuming I don't know this and can't use requestJSON.address
{
"userID": "aaaa1111",
"timestamp": 1649677057,
"address": "Elm Street",
"name": "Glen"
}

You can use the spread operator, for example:
const data = {
address: "Elm Street",
name: "Glen",
};
const item = {
userID: "aaaa1111",
timestamp: 1649677057,
...data,
};
console.log("item:", item);

If you insist on the API contract as
{
"userID": "aaaa1111",
"timestamp": 1649677057,
"data": {
"address": "Elm Street",
"name": "Glen"
}
}
then you can do mapping on the TypeScript level
const request: {userID: string, timestamp: number, data: any} = {
"userID": "aaaa1111",
"timestamp": 1649677057,
"data": {
"address": "Elm Street",
"name": "Glen"
}
};
const ddbObject: any = {
"userID": request.userID,
"timestamp": request.timestamp
};
Object
.keys(request.data)
.forEach(key => ddbObject[key] = request.data[key]);
Representation of ddbObject is
{
"userID": "aaaa1111",
"timestamp": 1649677057,
"address": "Elm Street",
"name": "Glen"
}

Adding data to a Json file using javascript

So I have an existing JSON file where the login data is stored. How can I add new users to this JSON file with JavaScript or JQuery?
This is my JSON-File:
{
"users": [
{
"username": "Tim",
"password": "test1"
},
{
"username": "Tom",
"password": "test2"
}
]
}

At the first put your data from login in data
var data = {
"users": [
{
"username": "Tim",
"password": "test1"
},
{
"username": "Tom",
"password": "test2"
}
]
}
And after that you shoud parse your json and put in jsonData and push your new user in it.
var jsonData = JSON.parse(data); //parse the JSON
jsonData.users .push({ //add new user
username :"Mohammad",
password :"test3",
});
At the end stringfy your json data to a string
data= JSON.stringify(jsonData);

Parse nested JSON Response Javascript

I know there are several threads on this subject but I've looked through over 30 threads without success.
I have managed to parse a JSON response so it looks like this:
{
"1": {
"id": "1",
"name": "Fruit",
.
.
.
"entities": {
"1": {
"id": "1",
"name": "blue bird",
.
.
.
"status": "1"
},
"2": {
using this code
let json = JSON.parse(body);
console.log(json);
Now I want to access the "id", "name" etc. AND the "id" and "name" for the "entities" tag.
So far I have tried:
console.log(json[0]);
console.log(json.id);
which both returns undefined
I have also tried
console.log(json[0].id);
which gives an error
Any ideas?

In this instance, your first key is 1, so you can access it with json[1].
const json = {
"1": {
"id": "1",
"name": "Fruit"
},
"2": {
"id": "2",
"name": "Veggies"
}
};
console.log(json[1]);

In this json, you can reach the id by
json.1.id
But I think that first of all your json is not correctly written, you should have something like
{
"elements": [
{ "id" : 1, "name" : "fruit" },
{ "id" : 2, "name" : "vegetable" }
]
}
like that, json.elements is a collection/array, and you can loop, count, or any other things you will not be able to do because your json looks like a super heavy list of different properties ( he doesn't know that json.1 and json.2 are the same type of objects.

const jsonData = JSON.parse(body);
for (const i in jsonData) {
for (const j in jsonData[i]) {
console.log('${i}: ${jsonData[i][j]}');
}
}

While retrieve a model by ID from a Backbone.js collection returning undefined

I'm trying to get a model from a collection by it's ID and display in view. After instantiating a model, I'm using the methods like get(), at() but it's returning undefined.
My collection:
[
{
"id": "1",
"firstname": "Abc",
"lastname": "Xyz"
},
{
"id": "2",
"firstname": "Klm",
"lastname": "Opq"
},
{
"id": "2",
"firstname": "rst",
"lastname": "Yvw"
}
]
Instantiation:
var persons = new PersonCollection();
console.log(persons.get(1)); // undefined
NOTE: I'm getting all the models in console (Not an issue). I want only to fetch a model by it's id name.

fetch is async so you need to place your code inside success callback
persons.fetch({
success: function() {
console.log('Now I have something: ', persons.get(1))
}
})
console.log('Nothing here: ', persons.get(1))
BTW to fetch single model by id you could use Model#fetch instead

Trouble parsing json with node.js

I wrote a quick script to parse two fairly large json file (~17k records) to do a comparison of the two. I have confirmed they are both valid json (via jsonlintpro) and the same format. (The source is the same so this should be a given. But, I always assume the mistake is mine. And I still do. Just somewhere else.) However, the parsed file just outputs [object, Object]. I'm wondering what the cause could possibly be?
The json format is like this small snippet (anonymized of course):
[
{
"id": "1234",
"name": "Name1",
"url": "https://localhost/Name1",
"date_created": "2013-07-05T18:47:05Z",
"date_cancelled": "",
"props": [
{
"id": "54321",
"type": "Client",
"value": "General Store"
},
{
"id": "65432",
"type": "Contact_Name",
"value": "Joe Smith"
}
]
},
{
"id": "23456",
"name": "Name2",
"url": "https://localhost/Name2",
"date_created": "2014-02-27T17:46:43Z",
"date_cancelled": "",
"props": [
{
"id": "34567",
"type": "Client",
"value": "Bait Shop"
}
]
}]
And here is the pertinent code:
var _ = require('underscore');
var recs = require('./prod.json');
printArr(recs);
console.log(recs.length);
function printArr(arr) {
arr.forEach(function(item) {
console.log(item + ", ");
});
}
Any guidance would be greatly appreciated.
UPDATE:
Ok, so apparently the issue is with my printArr function. I'm not sure what I'm doing wrong there. I'd like to figure it out because I want to expand upon that so I can print selectively.

the parsed file just outputs [object, Object].
This is the expected behavior BECAUSE you are concatenating an object with a string.
Try console.log(item) instead

console.log(item); should indeed print [object, Object], did you try to output its properties instead?
function printArr(arr) {
arr.forEach(function(item) {
console.log( item.id, item.name, item.url, item.date_created, item.date_cancelled, item.props, ';');
});
}

Just export the value from the prod.json file.
prod.json file
module.exports = [
{
"id": "1234",
"name": "Name1"
},
{
"id": "1234",
"name": "Name1"
}]
elsewhere
var recs = require('./prod.json')
console.log(recs)