In lambda, Could not parse request body into json - node.js

Question

I try to make backend with lambda.
So I make the sample of it and post the data by postman.
I select form-data and put data in key and value.
and it returns like that.
{"message": "Could not parse request body into json: Unrecognized token \'Idx\': was expecting \'null\', \'true\', \'false\' or NaN\n at [Source: [B#745d4999; line: 1, column: 5]"}
So I find the some of docs, if I use postman to test lambda, select row and post the data like
{
"key" : "params"
}
But I want to receive the data in lambda when I post the data by form-data type.
It is simple test of it
In lambda,
exports.handler = (event, context, callback) => {
// TODO implement
const Idx = event.Idx * 2;
callback(null, Idx);
};
and, when I post the data json type
and when I post the data form-data type

Answer 1

When using form data your event.body is not a JSON, it’s a string that you need to parse. Specifically, it’s a query string. So in your case, it is:Idx=2
What you need to do is parse it to a JSON and then operate on it.
You can use a module for that
const querystring = require('querystring');
And inside the lambda
const body = querystring.parse(event.body)
Now you can access the Idx using body[‘Idx’]
You can use typeof to differentiate if it is an object or a string like so:
if (typeof(event.body) === ‘object’)
Edit: full code
const querystring = require('querystring');
exports.handler = (event, context, callback) => {
// TODO implement
console.log(event.body);
var Idx = null;
if (typeof(event.body) === ‘object’) {
Idx = event.Idx * 2;
} else if (typeof(event.body) === ‘string’) {
Idx = querystring.parse(event.body)[‘Idx’];
}
callback(null, Idx);
};