AI solution for JavaScript Quiz on BFE.dev
108. property key

The code will output:

a
b

Explanation:

• const obj = {}: initializes an empty object.
• const a = { name: 'a'}: initializes an object with a property 'name' and value 'a'.
• const b = { name: 'b'}: initializes a different object than 'a' with a property 'name' and value 'b'.
• obj[a] = {...a}: sets the property with key 'a' in object 'obj' to a new object that copies all properties from object 'a' using the spread operator. In this case, the key is not the string 'a', but the object 'a' itself. JavaScript coerces object keys to strings before using them as property names. So, this statement is effectively equivalent to obj['[object Object]'] = {...a}.
• obj[b] = {...b}: sets the property with key 'b' in object 'obj' to a new object that copies all properties from object 'b' using the spread operator. Similarly, this statement is effectively equivalent to obj['[object Object]'] = {...b}.
• console.log(obj[a].name): gets the value of the 'name' property of the object stored in the property of 'obj' whose key is 'a' (which is really the same as the object stored with the key '[object Object]'). This value is 'a', so 'a' is logged to the console.
• console.log(obj[b].name): does the same for the object stored with the key 'b', which is '[object Object]' as well. This value has a 'name' property with the value 'b', so 'b' is logged to the console.