How to use an array of keys to fetch the value from a Javascript object

Question

If there is a Javascript object with multiple levels, as in:

myObject = {
        a: 12,
        obj11: {
                obj111: 'John',
                b:13,
                obj1111: { a:15, b: 35 } 
        },
        obj21: { 
                a:15,
                b:16 }
        }

I want to write a function to which is passed the object and an array of keys. The function should return a value based upon these keys. For example, passing [obj11,b] should return 13. Passing [obj11, obj1111,a] should return 15. Passing obj21 should return the object {a:15, b:16}

  function (myObj,myArr) {

      return keyVal;
  }

Assuming that the keys are always correct, can anyone help me solve this problem?

Answer 1

You can do this with a reduce() one-liner. Of course if you want to wrap it in a function, you can do that too.

 var myObject = { a: 12, obj11: { obj111: 'John', b:13, obj1111: { a:15, b: 35 } }, obj21: { a:15, b:16 } } var arr = ['obj11','b'] var val = arr.reduce((acc,curr) => acc[curr], myObject) console.log(val) var arr = ['obj11','obj1111', 'b'] var val = arr.reduce((acc,curr) => acc[curr], myObject) console.log(val) 

Answer 2

You could reduce the array with the keys and take an object as default value.

 function getValue(object, path) { return path.reduce(function (r, k) { return (r || {})[k]; }, object); } var object = { a: 12, obj11: { obj111: 'John', b: 13, obj1111: { a: 15, b: 35 }, obj21: { a: 15, b: 16 } } }; console.log(getValue(object, ['obj11', 'b'])); console.log(getValue(object, ['obj11', 'obj1111', 'a'])); console.log(getValue(object, ['obj11', 'obj21'])); 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 3

To increment the discussion, if you're using lodash you can also use the function _.get to get the value like this:

_.get(myObject, ['obj111', 'obj1111'])
//returns 'John'

If you object has properties with array values you can also get by indexes

var obj = {
        a: 1,
        b:[{
           d:4,
           c:8
        }]

_.get(obj, ['b','0','d'])
//returns 4

Source: https://lodash.com/docs/4.17.4#get