Why Are Two Identical Objects Not Equal To Each Other

When working with programming languages like JavaScript, you may come across a common question: Why are two identical objects not equal to each other? This phenomenon can seem perplexing at first, but understanding the underlying concepts can help clarify this behavior.

In programming, objects are instances of classes or structures that hold data and methods. When you create two objects with the same properties and values, they may appear identical on the surface. However, when you compare these objects using the equality operator '==', they may not evaluate to true.

This behavior occurs because objects in programming languages are reference types. When you create an object in memory, a reference to that object's location is stored in a variable. When you create another object with the same properties, even if they look the same, they are stored at different memory locations, meaning they are distinct objects.

To compare objects for equality in JavaScript, you can use the '===' operator. The triple equals operator checks for both value equality and type equality, ensuring that the objects being compared are of the same type and have the same values. This is known as strict equality comparison.

Here's a simple example in JavaScript to illustrate this concept:

let obj1 = { key: "value" };
let obj2 = { key: "value" };

console.log(obj1 == obj2); // Output: false
console.log(obj1 === obj2); // Output: false

In this example, obj1 and obj2 may have the same key-value pairs, but they are distinct objects in memory, leading to the comparison results being false.

If you want to compare two objects based on their properties, you will need to iterate over the object properties and compare them individually. This can be achieved using a function like the one below:

function compareObjects(obj1, obj2) {
  const keys1 = Object.keys(obj1);
  const keys2 = Object.keys(obj2);

  if (keys1.length !== keys2.length) {
    return false;
  }

  for (let key of keys1) {
    if (obj1[key] !== obj2[key]) {
      return false;
    }
  }

  return true;
}

let obj1 = { key: "value" };
let obj2 = { key: "value" };

console.log(compareObjects(obj1, obj2)); // Output: true

In this function, we iterate over the keys of both objects and compare their values. If all key-value pairs are the same, the function returns true, indicating that the objects are equal based on their properties.

Understanding why two identical objects are not equal in programming languages can help you write more robust and accurate code. By considering the underlying principles of how objects are stored and compared, you can avoid unexpected behavior and ensure that your comparisons yield the desired results.