Processing a JSON file using JSONata in Node.JS returns undefined. Why is this happening?

I tried this but it's returning "undefined"

index.js

    const jsonata = require("jsonata");
    const fs = require("fs");

    (async () => {
        const json = fs.readFileSync("test.json", {encoding:'utf8', flag:'r'});
        const expression = jsonata('V1.fields');
        const result = await expression.evaluate(json);
        console.log(result);
    })()

test.json

[
  12345,
  {
    "V1": {
      "fields": {
          "id": 0
      }
    }
  }
]

output

% node index.js  
undefined

https://try.jsonata.org/N02gm7EYz

CodePudding user response：

Despite its name, jsonata doesn't evaluate JSONs, it evaluates objects. You need to parse the JSON being read before passing it to jsonata.

You could do this explicitly:

const json = JSON.parse(fs.readFileSync("test.json", {encoding:'utf8', flag:'r'}));

But to be honest, it's easier to just require it and let Node.js do the "heavy" lifting:

const json = require("./test.json");