Recursive hasOwnProperty for objects

Question

I have an object as:

const object = {};
object.property1 = 54;
object.property1.property1 = 60;

now I would like to achieve something like this:

if(object.hasOwnProperty('property1')){
//do something
}
else if(object.hasOwnProperty('property1').hasOwnProperty('property1')){
//do something
}
else{
//do something
}

But it fails at the else if part. why can't we use hasOwnProperty recursively? what is the workaround? I am stuck at this for many hours now.

I have tried to use:

if(object.property1.property1){
//do something
}

but this gives me undefined

So how to get around this situation? Please help!

Is there any work around for this? the thing that I want to achieve? — , Jan 27 '23 at 14:26
The value of `object.property1` is a number. Numbers cannot have properties. — Pointy, Jan 27 '23 at 14:26
yeah I get it but is there any other method that we can use to check if the property1 exists in the property1 of the json object? — , Jan 27 '23 at 14:29
`object.property1.hasOwnProperty("name")` will be `true` if the value of `object.property1` has a property called "name". — Pointy, Jan 27 '23 at 14:32
what do you mean by `//do something` ? assign a value ? or are you expecting a kind of super switch ? your question is unclear... — Mister Jojo, Jan 27 '23 at 15:49

score 2 · Accepted Answer · answered Jan 27 '23 at 14:33

2

I would use a recursive function

const object = {};
object.property1 = {};
object.property1.property2 = 60;

if (hasOwnPropertyRecursive(object, 'property2')) {
  console.log('yes')
} else {
  console.log('no')
}

function hasOwnPropertyRecursive(obj, prop) {
  if (typeof obj !== 'object' || obj === null) return false
  if (obj.hasOwnProperty(prop)) return true
  return Object.getOwnPropertyNames(obj).some(key => hasOwnPropertyRecursive(obj[key], prop))
}

answered Jan 27 '23 at 14:33

Konrad

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will using `hasOwn` be more helpful or is `hasOwnProperty` good in this case? – Jan 27 '23 at 14:39
1

Use `Object.prototype.hasOwnProperty.call(obj, prop)` instead in case the object has [done something weird](https://stackoverflow.com/questions/12017693/why-use-object-prototype-hasownproperty-callmyobj-prop-instead-of-myobj-hasow) with its `hasOwnProperty` method. – kelsny Jan 27 '23 at 14:41

Mister Jojo · Answer 2 · 2023-01-27T18:09:34.237

@MisterJojo I am trying to assigning a value

so you may do that this way...

const 
  objA = {}
, objB = { propX: 'b' } 
, objC = { propX: { propX: 'c' } }
  ;
setLastProp( objA, 'propX', 'x_A' );
setLastProp( objB, 'propX', 'x_B' );
setLastProp( objC, 'propX', 'x_C' );

console.log( 'objA ->', JSON.stringify( objA ));
console.log( 'objB ->', JSON.stringify( objB ));
console.log( 'objC ->', JSON.stringify( objC ));



function setLastProp  ( obj, propName, value )
  {
  let next = obj, prev = obj, count = 0;
  while (next.hasOwnProperty(propName)) 
    {  
    prev = next;
    next = next[propName];
    };
  prev[propName] = value;
  }

Recursive hasOwnProperty for objects

2 Answers2