getting error when modifying the javascript property using Object.defineProperty()

Question

obj = [{
    prop11: 'value1',
    prop21: 'value2'
  },
  {
    prop12: 'value1',
    prop22: 'value2'
  },
  {
    key3: {}
  }
];

obj.forEach(element => {
  Object.defineProperty(obj.key3, 'prop1', {
    value: "xx",
    writable: true,
    enumerable: true,
    configurable: true
  })
});
console.log(obj.prop1)

getting error - Uncaught TypeError: undefined is not a non-null object tried several ways of this and also Object.defineProperties() but couldn't get working.

Answer 1

You need to correctly access key3 in your obj array and then define the property on it, To do so you need to find the object within the array that contains the key3 property after that create/define the property you need in the key3 object.

Refer the code below for reference:

let obj = [{
    prop11: 'value1',
    prop21: 'value2'
  },
  {
    prop12: 'value1',
    prop22: 'value2'
  },
  {
    key3: {}
  }
];


const key3Object = obj.find(element => element.key3); // get the object containing key3

if (key3Object && key3Object.key3) {
  Object.defineProperty(key3Object.key3, 'newProperty', {
    value: "newPropertyValueHere",
    writable: true,
    enumerable: true,
    configurable: true
  });
}

console.log(JSON.stringify(key3Object.key3.newProperty));