How to Check If Variable Is Object or String in Javascript

In JavaScript, it is often necessary to determine the type of a variable to perform appropriate operations or validations. One common scenario is checking whether a variable is an object or a string. In this article, we will explore various methods to achieve this in JavaScript.

To check if a variable is an object or a string in JavaScript, you can use the typeof operator and the constructor property. Additionally, the Object.prototype.toString.call() method provides a reliable approach. We will demonstrate each method with examples.

Method 1: Using the typeof Operator

The typeof operator is commonly used to determine the primitive type of a variable. However, it also provides information about certain built-in objects. Let’s consider an example:

let variable = {}; // An object
let type = typeof variable;

console.log(type); // Output: "object"

Here, the typeof operator returns “object” when applied to an object. However, it is important to note that this method does not differentiate between various object types.

Method 2: Using the constructor Property

Another approach to check if a variable is an object or a string is by using the constructor property. This property references the constructor function used to create an object. Consider the following example:

let variable = "Hello"; // A string
let isString = variable.constructor === String;
let isObject = variable.constructor === Object;

console.log(isString); // Output: true
console.log(isObject); // Output: false

In this example, we compare the constructor property of the variable with the String and Object constructor functions. If the comparison returns true, it means the variable is of that specific type.

Method 3: Using Object.prototype.toString.call()

The most reliable way to determine if a variable is an object or a string is by using the Object.prototype.toString.call() method. This method provides a consistent output across different JavaScript environments. Let’s see an example:

let variable = "Hello"; // A string
let type = Object.prototype.toString.call(variable);

console.log(type); // Output: "[object String]"

By invoking toString.call() on an object or a string, we obtain a string representation that includes its type enclosed within square brackets. This allows us to easily identify whether the variable is an object or a string.

Conclusion

In this article, we explored various methods for checking if a variable is an object or a string in JavaScript. We discussed using the typeof operator, the constructor property, and the Object.prototype.toString.call() method. Each method provides an effective way to determine the type of a variable, but the latter two methods are more reliable in differentiating between objects and strings.

Remember to choose the appropriate method based on your specific requirements. Happy coding!