Access elements inside json object without knowing names

Question

I have the following json object in node.js.

x={
    '40': {
        length: '2',
        data: ['11', '22']
    },
    '41': {
        length: '1',
        data: ['fe']
    },
    '42': {
        length: '2',
        data: ['ef', 'ab']
    },  
}

Suppose I do not know in advance what will be the property name inside x. However, I would like to retrieve every property and its associated value. How can this be done?

I am using node.js

Answer 1

Use recursion to find the key/values of all objects nested or otherwise:

function finder(obj) {

  // for each property in the object passed into
  // the function...
  for (var p in obj) {

    // if its value is another object (see appended note)...
    if (Object.prototype.toString.call(obj[p]).slice(8, -1) === 'Object') {

      // ...log the key to the console and then call finder()
      // again with this current object (this is the recursive part)
      console.log('key: ' + p + ', value: Object');
      finder(obj[p]);

    // otherwise log the key/value
    } else {
      console.log('key: ' + p + ', value: ', obj[p]);
    }
  }
}

finder(x);

OUTPUT

key: 40, value: Object
key: length, value:  2
key: data, value:  Array [ "11", "22" ]
key: 41, value: Object
key: length, value:  1
key: data, value:  Array [ "fe" ]
key: 42, value: Object
key: length, value:  2
key: data, value:  Array [ "ef", "ab" ]

NOTE

This rather long-winded line of code to check if a value is an object

Object.prototype.toString.call(obj[p]).slice(8, -1) === 'Object'

is necessary because typeof obj[p] === 'object' will return true for arrays and null too. It's a bit of a gotcha.

Object.prototype.toString.call({})

returns a string like "[object Object]", and the slice grabs the relevant section of the string.