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.