I have to write a utility function which reads a dynamodb item and returns a flattened version of that record.
Sample Item
const data={
"node": {
"S": "someKey"
},
"payload": {
"M": {
"name": {
"S": "some_name"
},
"phone": {
"M": {
"0": {
"S": "+126526562562"
},
"1": {
"S": "+126512651652"
}
}
},
"country": {
"S": "US"
}
}
}
}
Below is the sample utility function .
const utility = (result, field) => {
const mapping = result[field];
const { M: data } = mapping;
const fieldTypes = ['N','S','M'];
return Object.fromEntries(
Object
.keys(data)
.map((key) => ({ fieldType: Object.keys(data[key]).shift(), key }))
.filter((o) => fieldTypes.includes(o.fieldType))
.map((o) => [o.key, data[o.key][o.fieldType]]),
);
};
console.log(flattenMap(data,'payload'))
This function works fine if there are no maps inside payload. For example, if I remove the phone attribute from dynamodb item , then I get { name: 'some_name', country: 'US' } which is correct but with phone, I get -
{
name: 'some_name',
phone: { '0': { S: '+126526562562' }, '1': { S: '+126512651652' } },
country: 'US'
}
whereas, what I expect is
{
name: 'some_name',
phone: { '0':'+126526562562' }, '1': '+126512651652' },
country: 'US'
}
What more do I need to add here so that I get the expected response even with a nested map inside payload.
The easy way: use the SDK v3 DynamoDB utilities to handle conversions:
import { convertToNative } from '@aws-sdk/util-dynamodb';
const converted = convertToNative(payload)
If you insist on DIY: use recursion to deal with arbitrary nesting. The utility function's logic should be invoked recursively for every value in the payload that is a DynamoDB "map" such as { S: '+126526562562' }.
Values are DynamoDB "maps" if they are key-value pairs with keys of ['N','S','M']:
if (val.constructor === Object && Object.keys(val).every(k => fieldTypes.includes(k))) {
// val is a DynamoDB map, call the function recursively on val
}