Why does it return false when comparing two similar objects in JavaScript?

In JavaScript, two objects are considered equal only if they are the same object, not just if they have the same properties and values. This is because, in JavaScript, objects are assigned and compared by reference, not by value. This means that when you compare two objects, you are actually comparing the references to those objects, not the objects themselves. If the two objects have the same properties and values but are not the same object, the comparison will return false.

Here is an example of how objects are compared by reference in JavaScript:

// Create two objects with the same properties and values
let obj1 = { name: "John", age: 25 };
let obj2 = { name: "John", age: 25 };
// Compare the two objects
console.log(obj1 == obj2); // returns false
console.log(obj1 === obj2); // returns false

As you can see in the code above, even though obj1 and obj2 have the same properties and values, the comparison returns false. This is because the objects are not the same object, they are just two separate objects with the same properties and values.

In order for the comparison to return true, the objects must be the same object, like this:

// Create an object
let obj = { name: "John", age: 25 };
// Create a reference to the object
let objRef = obj;
// Compare the object and its reference
console.log(obj == objRef); // returns true
console.log(obj === objRef); // returns true

In the code above, obj and objRef are the same object, so the comparison returns true. This is because objRef is a reference to the obj object, so the comparison is actually comparing the same object.

To compare the properties and values of two objects in JavaScript, you can use the Object.keys() method to get the properties of each object, and then compare the values of those properties. Here is an example:

// Create two objects with the same properties and values
let obj1 = { name: "John", age: 25 };
let obj2 = { name: "John", age: 25 };
// Get the properties of each object
let obj1Props = Object.keys(obj1);
let obj2Props = Object.keys(obj2);
// Compare the number of properties
if (obj1Props.length != obj2Props.length) {
console.log("The objects have a different number of properties");
} else {
// Compare the values of each property
let allPropsAreEqual = true;
for (let i = 0; i < obj1Props.length; i++) {
let propName = obj1Props[i];
if (obj1[propName] !== obj2[propName]) {
allPropsAreEqual = false;
break;
}
}
if (allPropsAreEqual) {
console.log("The objects have the same properties and values");
} else {
console.log("The objects have the same properties but different values");
}
}

In the code above, the Object.keys() method is used to get the properties of each object, and then the values of those properties are compared to determine if the objects are equal.


October 28, 2022
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