How to check if a value is object-like in JavaScript?

In JavaScript, Object-likeA value is a value that is not primitive and is not undefined. An object-like value is any value that is not a primitive, including functions, arrays, and objects. There are different ways in JavaScript to check if a value is an object. In this article, we will introduce 3 ways to check if a value is a class object in JavaScript.

Using the typeof operator

typeof The typeof operator is a built-in operator in JavaScript that is used to check the type of a value. The typeof operator returns a string that is the type of the value. The typeof operator can be used to check whether a value in JavaScript is similar to an object.

Example 1

Here is a detailed explanation of the above code snippet:

In the first statement in the script tag, we are checking for an empty object {} type. this The typeof operator returns the string "object" of the empty object. In the second statement, We are checking the type of empty array []. typeof operator returns a string "object" means an empty array. In the third statement we are checking the type of an Anonymous function function(){}. The typeof operator returns the string "function" Anonymous function.

Use the instanceof operator:

The instanceof operator is a built-in operator in JavaScript that is used to check whether a value Is an instance of a constructor function. instanceof operator returns a boolean value value, true if the value is an instance of the constructor; value is not an instance of the constructor. You can use the instanceof operator Check if a value in JavaScript is object-like.

Example 2

In the script tag, in the first statement, we check if the empty object {} is a Instance of object constructor. instanceof operator returns The Boolean value true for an empty object. In the second statement we check whether Empty array[] is an instance of the Array constructor. instance operator Returns Boolean true for an empty array. In the third statement we are checking If the anonymous function function(){} is an instance of the Function constructor. For anonymous functions, the instanceof operator returns the Boolean value true.

Object.prototype.toString() method:

Object.prototype.toString() method is a built-in method in JavaScript for converting objects to strings . The Object.prototype.toString() method can be used to check whether a value in JavaScript is object-like.

Example 3

In the first statement within the script tag, we use The Object.prototype.toString() method converts an empty object {} to a string. this The Object.prototype.toString() method returns the string "[object Object]" Empty object.