Fetching data from a web server is a common task in modern web development. JavaScript’s Fetch API is a powerful tool for making HTTP requests to a server and fetching data. However, sometimes you need to pass parameters in the request URL to get accurate responses from the server. Here, we will learn how to use the Fetch API to send GET requests with parameters and how to handle the response.
In this article, we will cover:
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Introduction to the Fetch API and GET requests.
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How to use the Fetch API to make GET requests with URL parameters.
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How to handle the server's response using the Fetch API.
Introduction to the Fetch API and GET requests
The Fetch API is a modern web API that provides a simple interface for making HTTP requests to a web server. The Fetch API is available in most modern browsers, and it works in Node.js through polyfills. The Fetch API has become the go-to method for making requests in JavaScript because it is simple to use and easy to understand.
GET requests are one of the most common types of HTTP requests. A GET request is used to retrieve data from a server. A GET request sends its parameters in the URL string. GET requests are idempotent, meaning that they will return the same response every time they are requested.
To make a GET request, you need to construct a URL with the necessary parameters. The server then responds with a JSON object containing the requested data. The URL parameters can be passed in the query string of the URL. For example, the query string of the following URL:
‘https://jsonplaceholder.typicode.com/comments?postId=1’
contains a parameter called postId with a value of 1.
How to use the Fetch API to make GET requests with URL parameters.
Let's create a function that fetches data from the above URL using the Fetch API and URL parameters.
function fetchData(postId){
fetch(`https://jsonplaceholder.typicode.com/comments?postId=${postId}`)
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.log(error.message))
}
In this example, we use the Fetch API to fetch data from the server. The fetch function takes a URL as its argument, which includes the parameter postId and its value. We use template literals to interpolate the value of postId into the URL. When the response is returned from the server, we use the response.json() method to convert the response to a JSON object. Finally, we log the data to the console.
To call this function with a different postId, you can pass the postId as a parameter.
fetchData(1) // fetches comments with postId=1
fetchData(2) // fetches comments with postId=2
How to handle the server's response using the Fetch API.
Once the Fetch API receives the response from the server, we need to parse the response and extract the relevant data. We can use the json() method to parse the JSON response returned by the server. We can then access the data by key/value pairs.
function fetchData(postId){
fetch(`https://jsonplaceholder.typicode.com/comments?postId=${postId}`)
.then(response => response.json())
.then(data => {
console.log("Data received:");
console.log(data);
console.log("Extracted comments:");
data.forEach(comment => console.log(comment.body));
})
.catch(error => console.log(error.message))
}
In this example, we use the forEach() method to iterate over the array of comments returned by the server. We use the comment.body property to extract the body of each comment and log it to the console.
Conclusion
We learned how to use the Fetch API to make GET requests with URL parameters and how to handle the server's response using the Fetch API. Fetching data from a server is an essential part of modern web development, and the Fetch API is a powerful and easy-to-use tool for making these requests. With a little knowledge of parameterized GET requests and the Fetch API, you can retrieve data from any server quickly and efficiently.
In this section, we will dive deeper into the previous topics discussed in the article.
Introduction to the Fetch API and GET requests:
The Fetch API is a modern, cross-platform way of sending and receiving data from servers using JavaScript. It provides a simple and consistent interface for making HTTP requests and for handling responses.
The Fetch API was introduced in ES6 (ECMAScript 2015), and it is intended to replace the old XMLHttpRequest (XHR) API. The Fetch API provides a much simpler and cleaner interface than the XHR API. It supports promises and enables better error handling.
GET requests are a type of HTTP request that retrieves data from a server. The parameters of a GET request are specified in the URL query string. The query string is the part of the URL that comes after the question mark (?).
For example, consider the following URL:
https://www.example.com/search?q=javascript&limit=20
In this URL, we have two parameters: q and limit. The value of q is “javascript”, and the value of limit is 20.
How to use the Fetch API to make GET requests with URL parameters:
To make a GET request with parameters using the Fetch API, we need to construct the URL with the parameters and then pass it to the fetch() function.
The fetch() function takes one argument, which is the URL to fetch. We can construct the URL by concatenating the base URL and the query string. We can use template literals to insert the parameter values into the URL.
const baseURL = 'https://api.example.com';
const query = '?userId=123&limit=10';
fetch(`${baseURL}/posts${query}`)
.then(res => res.json())
.then(data => console.log(data));
In this example, we constructed the URL by concatenating the base URL and the query string. We then passed the URL to the fetch() function. Finally, we used the json() method to extract and parse the response.
How to handle the server's response using the Fetch API:
The Fetch API returns a Promise that resolves to a Response object. The Response object contains a large number of properties and methods that allow us to extract data from the response.
We can use the json() method to extract JSON data from the response. The json() method returns a Promise that resolves to the parsed JSON data.
fetch(url)
.then(response => response.json())
.then(data => {
// Use the data
})
.catch(error => {
// Handle the error
});
In this example, we used the json() method to extract and parse the JSON data from the response. We then accessed the parsed data in the second then() method and handled any errors in the catch() method.
Conclusion:
In this article, we’ve learned about the Fetch API and how to use it for making GET requests with parameters. We’ve also learned about how to handle the server's response using the Fetch API. The Fetch API is a powerful and easy-to-use API for making HTTP requests in modern web development. It supports promises and allows for better error handling than the old XMLHttpRequest (XHR) API. With the Fetch API, we can fetch data from servers and work with it in our web applications.
Popular questions
- What is the Fetch API?
The Fetch API is a modern web API that provides a simple interface for making HTTP requests to a web server. It simplifies the syntax of making HTTP requests in JavaScript and can be used to fetch data from a server.
- How do you make a GET request to a server using the Fetch API and URL parameters?
To make a GET request with parameters using the Fetch API, you need to construct the URL string with the necessary parameters and pass it to the fetch() method. You can use template literals to insert the parameter values into the URL. For example:
const baseURL = 'https://api.example.com';
const query = '?userId=123&limit=10';
fetch(`${baseURL}/posts${query}`)
.then(res => res.json())
.then(data => console.log(data));
- How does the Fetch API handle server responses?
The Fetch API returns a Promise that resolves to a Response object containing a large number of properties and methods that help to extract data from the response. You can use the json() method to extract and parse the JSON data from the response.
fetch(url)
.then(response => response.json())
.then(data => {
// Use the data
})
.catch(error => {
// Handle the error
});
- What is a query string?
A query string is part of a URL that specifies additional parameters and values to be sent with the HTTP request. The query string is indicated by the question mark (?) character in the URL, followed by a list of key-value pairs. For example:
https://www.example.com/search?q=javascript&limit=10
In this example, the query string specifies two parameters: q with a value of "javascript" and limit with a value of 10.
- Why is the Fetch API preferred over the XMLHttpRequest (XHR) API?
The Fetch API is preferred over the XMLHttpRequest (XHR) API because it provides a simpler and cleaner interface for making HTTP requests with JavaScript. The Fetch API uses promises, which make it easier to handle asynchronous operations, and it allows for better error handling. The Fetch API is also a newer API that is gaining in popularity and support, while the XMLHttpRequest (XHR) API is an older API with more complex syntax and less consistent cross-browser support.
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