JSON.stringify replacer - how to get full path

Question

Replacer in below code write on console current processed field name

Answer 1

You can use custom walk function inside your replacer. Here's an example using a generator walk function:

const testObject = {a: 1, b: {a: 11, b: {a: 111, b: 222, c: 333}}, c: 3};

function* walk(object, path = []) {
    for (const [key, value] of Object.entries(object)) {
        yield path.concat(key);

        if (typeof value === 'object') yield* walk(value, path.concat(key));
    }
}

const keyGenerator = walk(testObject);

JSON.stringify(testObject, (key, value) => {
    const fullKey = key === '' ? [] : keyGenerator.next().value;

    // fullKey contains an array with entire key path
    console.log(fullKey, value);

    return value;
});

Console output:

  fullKey          |  value
-------------------|------------------------------------------------------------
  []               |  {"a":1,"b":{"a":11,"b":{"a":111,"b":222,"c":333}},"c":3}
  ["a"]            |  1
  ["b"]            |  {"a":11,"b":{"a":111,"b":222,"c":333}}
  ["b", "a"]       |  11
  ["b", "b"]       |  {"a":111,"b":222,"c":333}
  ["b", "b", "a"]  |  111
  ["b", "b", "b"]  |  222
  ["b", "b", "c"]  |  333
  ["c"]            |  3

This works, assuming the algorithm in replacer is depth-first and consistent across all browsers.