How to compare objects in JavaScript

In JavaScript, there are different ways to compare objects, depending on what you want to achieve. Below are some methods you can use to compare objects in JavaScript:

The == and === Operators:

The == and === operators are used to compare the values of two objects. The == operator compares the values of the two objects, while the === operator compares the values and types of the two objects.

For example:

Output:

false
false

In this example, even though obj1 and obj2 have the same properties and values, they are not equal since they are different objects.

The Object.is() Method:

The Object.is() method compares two objects for equality. It returns true if the objects are equal, and false if they are not. The Object.is() method is similar to the === operator but handles some special cases differently, such as NaN and -0.

For example:

Output:

false

In this example, Object.is() returns false since obj1 and obj2 are not the same object.

The JSON.stringify() Method:

The JSON.stringify() method converts an object into a string. If two objects have the same properties and values, their resulting strings will be identical. You can use this to compare two objects by converting them to strings and comparing the strings.

For example:

Output:

true

In this example, JSON.stringify() is used to convert obj1 and obj2 into strings, which are then compared.

Custom Comparison Function:

If you have specific requirements for comparing objects, you can define a custom comparison function. For example, you may want to compare objects based on their properties or values in a specific order. In this case, you can define a function that takes two objects as parameters and returns a value indicating their order.

For example:

Output:

-1

In this example, compareObjects() is a custom function that compares two objects based on their a property. The function returns -1 if obj1.a is less than obj2.a, 1 if obj1.a is greater than obj2.a, and 0 if they are equal.

Manual comparison:

Reading the attributes and manually comparing them is a straightforward method for comparing things based on content.

Let's create a custom function called isHeroEqual() to compare two hero instances.

For example:

Output:

true
false

The isHeroEqual() reads the names of the two objects' properties and contrasts their values.

We prefer to build comparison functions like isHeroEqual, if the compared objects have a few characteristics. These functions run well since there aren't many property accessors and equality operators used in the comparison.

For basic objects, manually extracting properties is not an issue. Manual comparison necessitates this. Nevertheless, the manual comparison is inconvenient when comparing larger items (or objects whose structure is unknown) because it necessitates writing a lot of boilerplate code.

Third-Party Libraries:

Finally, there are many third-party libraries that provide more advanced object comparison functionality. Some popular ones include Lodash, Underscore, and Ramda. These libraries provide a wide range of utility functions that can be used to compare objects in various ways, such as deep comparison, equality by value, and comparing objects based on certain properties. For example, in Lodash you can use the isEqual() function to compare

Summary:

If the operands are different object instances, it can be shown using referential equality (using ===, ==, or Object.is()).

The manual equality check necessitates manually comparing the values of the characteristics. Despite the fact that this check necessitates manually writing down the characteristics to be compared, we like this method's simplicity. A preferable strategy is to perform a shallow check if the objects being compared have numerous characteristics or if the structure of the objects is determined at runtime. Lastly, the deep equality check should be used if the compared objects comprise nested objects.