How to create a JSON array that works for all types(String, number)?

Hi Forum,

I need to create a JSON array by capturing values from the previous snap. Basic requirement is as below:

Input:

[
    {
        "prop1": "abc",
        "prop2": "2",
        "prop3": null
    }
]

Output:

[
    {
        "custom_fields": [
            {
                "id": 1,
                "value": "abc"
            },
            {
                "id": 2,
                "value": 2
            },
            {
            	"id" : 3
            	"value" : null
            }
        ]
    }
]

The JSON array should work for all data types(string, null and number). so I created a simple pipeline with mapping logic as :
JSON.parse('[{"id": 1, "value": '+ $prop1 + '}, {"id": 2, "value": ' + $prop2 + '}, { "id" : 3, "value" : '+ $prop3 +' } ]')

But it throws error

Failure: Unable to parse JSON value, Reason: Unrecognized token ‘abc’: was expecting (‘true’, ‘false’ or ‘null’), Resolution: Please check the format of the JSON value

Here is the sample pipeline:

1_2017_08_16.slp (3.5 KB)