This post will discuss how to get contents of a URL into a string in JavaScript.

There are several ways to get the contents of a URL into a string in JavaScript. Reading the contents of a URL can be useful for fetching data from web pages, APIs, or other sources. Here are some of the most common functions:

1. Using XMLHttpRequest object

One way to get the contents of a URL into a string in JavaScript is to use the XMLHttpRequest object, which can send and receive data from a server. We can create an instance of this object, open a GET request with the URL, and access the responseText property after the request is completed. Here’s an example:

Download Code

 
However, this function has some limitations and drawbacks. For instance, it may not work for cross-origin requests, which are requests to URLs that have a different domain, protocol, or port than the current page. This is because of the same-origin policy, which restricts how a document or script loaded from one origin can interact with a resource from another origin. To overcome this restriction, we may need to use other techniques, such as JSONP or CORS.

 
Another limitation of this function is that it uses a synchronous request, which means that the code execution will block until the request is completed. This can have negative effects on the user experience and performance of our web page. To avoid this, we may want to use an asynchronous request, which means that the code execution will continue without waiting for the response. To do this, we need to pass true as the third argument of the open function, and provide a callback function that will handle the response when it is ready. Here’s an example:

Download Code

2. Using jQuery

Another option is to use a library or framework that simplifies the process of making HTTP requests in JavaScript. One popular example is jQuery, which is a popular JavaScript library that provides many useful functions for manipulating HTML, making AJAX requests, and more. jQuery provides a $.ajax() function that can handle different types of requests and data formats. We can use this function to get the contents of a URL into a string by specifying the URL, the type of request (GET), and a success function that will receive the response as an argument. Here’s an example:

Download Code

 
Alternatively, we can directly use jQuery’s $.get() function to send a HTTP GET request to a URL and get the contents as a string. The $.get() function accepts two arguments: the URL and a callback function. The callback function is executed when the request is successful, and receives one parameter: data, which contains the contents of the URL as a string. The following code illustrates this:

Download Code

 
However, jQuery also has some limitations and drawbacks. For instance, it may not work for cross-origin requests unless we use some additional techniques, such as YQL or jsonpCallback. Moreover, jQuery may not be necessary if we only want to make simple HTTP requests, since modern browsers support native functions that can achieve the same functionality.

3. Using Fetch API

One such native function is fetch(), which is part of the Fetch API that provides an interface for fetching resources across the network. We can use this function to get the contents of a URL into a string by passing the URL as an argument, and using the then function to chain promises that will process the response. The following code uses the fetch() function with the URL as an argument, and returns a promise that resolves to a response object. The code then calls the text() function on the response object, which returns another promise that resolves to a string containing the contents of the URL. The code then logs the data as a string, or handles any errors that may occur.

Download Code

 
The fetch() function is a modern and easy way to make HTTP requests, and has some advantages over XMLHttpRequest and jQuery. For instance, it supports both synchronous and asynchronous requests, it has a cleaner and more readable syntax, and it can handle different types of responses, such as JSON or Blob. However, it also has some disadvantages. For example, it does not support older browsers that do not implement the Fetch API, it does not reject promises on HTTP errors (such as 404 or 500), and it does not send cookies by default.

Therefore, depending on our use case and requirements, we may want to choose the most suitable function for reading the contents of a URL into a string in JavaScript. There is no definitive answer to this question, as each function has its own pros and cons. We may also want to consider other factors, such as security, performance, compatibility, and readability, when making our decision.