How To Use Contains In Javascript?

In this post we will be discussing how to use the contains function in javascript. This function is used to check if a string contains another string.

Checkout this video:

Introduction to the contains method in Javascript

The .contains() method returns true if the DOM element provided as the first argument contains the second argument. For example, given the following HTML:

“`

Hello world!

“`
The following code would return true:
“`javascript
document.getElementById(“myDiv”).contains(document.querySelector(“span”)); // returns true
“`

Why use the contains method in Javascript?

The .contains() method returns true if the DOM element provided as the first argument contains the element provided as the second argument. This method is supported in all major browsers, including Internet Explorer 9 and higher.

The .contains() method is especially useful for determining whether an element is a descendant of another element, without having to traverse all of the ancestors of the element.

How to use the contains method in Javascript?

The contains method in Javascript can be used to check if a given string contains another string. For example, you can use it to check if a given string contains a certain word or phrase. To use the contains method, you first need to create a new String object and then call the contains method on that String object, passing in the string you want to check for as an argument. Here’s an example:

var str = “this is a teststring”;

if (str.contains(“test”)) {
console.log(“The string contains the word ‘test’!”);
} else {
console.log(“The string does not contain the word ‘test’!”);
}

A real world example of using the contains method in Javascript

In this article, we will take a look at a real world example of how to use the contains method in Javascript.

First, let’s say we have an array of objects that represent different people:

var people = [
{name: ‘John’, age: 21},
{name: ‘ Jane’, age: 29},
{name: ‘ Bob’, age: 31}
];

Now let’s say we want to find out if the array contains an object with the name ‘John’. We can do this by using the Array.prototype.contains() method:

var contained = people.contains({name:’John’}); // true

Why you should avoid using the contains method in Javascript

When working with arrays in Javascript, you may have come across the contains method. This method returns true if the array contains the element you are looking for, and false if it does not. While this method may seem convenient, there are a few reasons why you should avoid using it.

First, the contains method is not supported by all browsers. In particular, Internet Explorer does not support this method. So if you need your code to work in all browsers, you should avoid using this method.

Secondly, even in browsers that do support the contains method, it can be slower than other methods of searching for an element in an array. So if performance is a concern, you should use a different method.

Finally, the contains method only works on arrays. If you try to use it on other data types ( such as a string or an object), it will not work. So if you need to search for an element in something other than an array, you should use a different method.

When to use the contains method in Javascript?

The .contains() method returns true if the DOM element provided as the parameter is a descendant of the element on which it is invoked (i.e., if it is found in the element’s subtree). Otherwise, it returns false.

Note: unlike .hasChildNodes() and .childElementCount, which look only at immediate children,
the .contains() method descent through all ancestors of the element on which it’s invoked.

One use case for .contains() is to check whether an element that you intend to remove from the DOM tree is currently attached/visible.

How not to use the contains method in Javascript

The contains method is used to check whether an element exists in another element or not. This can be done by traversing through the array and checking each element against the given element.

However, this method should not be used in Javascript as it is slower than other methods.

A final word on using the contains method in Javascript

The contains method is a convenient way to check if a given string contains a certain substring. It can be used with both regular strings and strings created using the String object. The contains method is case-sensitive, so keep that in mind when using it.

One common use for the contains method is to check if a given string is empty. To do this, simply call the contains method with an empty string as the argument. The method will return true if the string is empty and false otherwise.

Another use for the contains method is to check if a given string contains only whitespace characters. This can be done by calling the trim method on the string before passing it to the contains method. The trim method removes all leading and trailing whitespace from the string, so if the resulting string is empty, you know that it contained only whitespace characters.

Further reading on the contains method in Javascript

The contains method returns a boolean value, indicating whether or not the provided string is found within the given string. This method is case-sensitive, meaning that it will return false if the provided string is not found exactly within the given string.

For example, let’s say we have a string “JavaScript” and we want to know if it contains the word “script”. We can use the contains method to do this:

var myString = “JavaScript”;
var searchTerm = “script”;

if (myString.contains(searchTerm)) {
// do something
}

How to use the contains method in other programming languages

In programming, the contains method is used to check whether a certain element is present in a given list or not. It returns a boolean value, meaning it will either return true or false.

This method is widely used in various programming languages such as Java, Python, C++, etc.

The syntax for using the contains method in each of these languages is different but the overall idea is the same.

In this article, we will take a look at how to use the contains method in both Java and Python. We will also discuss the differences between these two programming languages when it comes to using this method.

Java:
The syntax for using the contains method in Java is as follows:

list.contains(element);
Here, list is the name of the list where we want to check if an element is present or not. The element can be of any data type such as an integer, string, character, etc.

The contains method will return a boolean value – true if the element is present in the list and false if it is not present.

Let’s take a look at an example to understand this better.

import java.util.*;

public class Main {

public static void main(String[] args)
{

// creating a list of strings
Listlist = new ArrayList();

// adding elements to the list
list.add(“Java”);
list.add(“Python”);
list.add(“C++”);

// checking if an element is present in the list or not
// using the contains() method
boolean flag = list.contains(“Java”);

if(flag) { System.outoutprintln(“List contains Java”); } else { System.”not Present”); } }} Output: List contains Java As you can see from the output, our program was able to successfully check if “Java” was present in the given list or not by using the contains method.

Scroll to Top