How to create nested JSON based on array of keys?

Question

Given input:

let input = [
  {
    schema: ["user", "email"],
    value: "test@test.com"
  },
  {
    schema: ["user", "name", "firstName"],
    value: "John"
  },
];

let output = {};

for (let i = 0; i < input.length; i++) {
    let data = input[i];

    for (let j = 0; j < data.schema.length; j++) {
        let s = data.schema[j];
        // How to set nested levels here ? eg: output["user"]["email"] = {};
    }
}

Expected output:

{
    "user": {
        "email": "test@test.com",
        "name": { 
            "firstName": "John" 
        }
    }
}

Here "schema" represents the nested structure in JSON for the data.

What is the approach for dynamically setting nested attributes using Javascript ?

What is `data.schema`? What about `output["user"]["email"] = {};` isn’t working? — Sebastian Simon, Feb 18 '18 at 11:58
@Xufox : I cannot use output["user"]["email"] since "user" and "email" will be dynamic. — Sudhir Shrestha, Feb 18 '18 at 12:00
Okay, then just replace `"user"` and `"email"` with the variables containing the dynamic strings. See [Using a variable for a key in a JavaScript object literal](https://stackoverflow.com/q/2274242/4642212). — Sebastian Simon, Feb 18 '18 at 12:07
It is represented as array eg: ["user", "email"] so I will need to loop to set it. Please refer to the example, I have updated it. — Sudhir Shrestha, Feb 18 '18 at 12:11

trincot · Accepted Answer · 2018-02-18T12:23:28.370

2

You could use reduce to "deepen" the output object until the level where the property/value needs to be set:

const input = [{schema: ["user", "email"],value: "test@test.com"},{schema: ["user", "name", "firstName"],value: "John"},];
const output = {};

for (const obj of input) {
    obj.schema.slice(0, -1).reduce(
        (acc, lvl) => acc[lvl] || (acc[lvl] = {}), 
        output
    )[obj.schema.slice(-1)[0]] = obj.value;
}

console.log(output);

This way it also works if the schema array has more than 2 values.

edited Feb 18 '18 at 12:23

answered Feb 18 '18 at 12:15

trincot

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The OP has changed the question's body! – Ele Feb 18 '18 at 12:21
Thanks for letting me know. Adapted the input in my answer accordingly. – trincot Feb 18 '18 at 12:24
1

Works flawlessly, Thank you :) – Sudhir Shrestha Feb 18 '18 at 12:24

How to create nested JSON based on array of keys?

1 Answers1