Interviewer: What is the difference and usage scenarios between GET and POST?

Interviewer: The difference between GET and POST and usage scenarios

1. What are GET and POST?

In the HTTP protocol, GET and POST are two commonly used request methods for sending requests to the server and getting responses. They have the following characteristics:

GET method

The GET method is used to request a representation of a specified resource, typically used to retrieve data, and should not have side effects on the server. The parameters of the GET request are appended to the URL.

POST method

The POST method is used to submit data to a specified resource to be processed, usually resulting in a state change on the server or side effects. The parameters of the POST request will be included in the body of the request.

Second, the difference between GET and POST

Although both GET and POST use the HTTP protocol to transmit data, they have obvious differences in some aspects:

1. Parameter position

Parameters for GET requests are appended to the end of the URL in the form:http://example.com/path?param1=value1&param2=value2

Parameters for POST requests are included in the body of the request and are not displayed in the URL.

2. Data length limitation

The parameters of the GET request are appended to the URL and are limited by the length of the URL. Generally, it is limited by the browser. Different browsers may have different restrictions. For example, IE is limited to 2083 bytes.

The parameters of the POST request are in the body of the request, and there is no clear length limit, which is generally limited by the configuration of the server.

3. Security

The parameters of the GET request will be displayed in the URL, so it is not advisable to use GET requests for sensitive information, because sensitive information may be saved by the browser, recorded in history, or viewed by others.

The parameters of the POST request are in the body of the request, which is relatively more secure, but it is still not absolutely safe, because HTTP is transmitted in plain text, and only HTTPS can be used to encrypt data transmission.

4. Cache and History

GET requests will be actively cached by the browser, but POST requests will not be cached unless manually set. Because the parameters of the GET request are appended to the URL, the browser will use the URL as a cache identifier.

5. Idempotence

GET requests are idempotent, if the same GET request is executed multiple times, the state of the server will not change.

POST requests are not idempotent, and multiple executions of the same POST request may produce different results because it may cause changes in the server state.

3. Usage scenarios of GET and POST

GET requests are mainly used to fetch data because it is idempotent and cacheable. Common usage scenarios include:

• search engine request
• Get web content
• Get resource files etc.

POST requests are primarily used to submit data to the server, as it may result in a state change or have side effects. Common usage scenarios include:

• submit form data
• upload files
• post a comment etc.

In practical applications, GET or POST methods should be selected according to specific needs, and rational use of them can improve application performance and security.

4. Example code

GET request example (JavaScript)

const url = "https://api.example.com/data?id=123";
fetch(url)
  .then(response => response.json())
  .then(data => {
    
    
    console.log(data);
  })
  .catch(error => {
    
    
    console.error("Error:", error);
  });

POST request example (JavaScript)

const url = "https://api.example.com/submit";
const data = {
    
    
  username: "user123",
  password: "pass456"
};
fetch(url, {
    
    
  method: "POST",
  headers: {
    
    
    "Content-Type": "application/json"
  },
  body: JSON.stringify(data)
})
  .then(response => response.json())
  .then(data => {
    
    
    console.log(data);
  })
  .catch(error => {
    
    
    console.error("Error:", error);
  });

The above example uses fetchfunctions to send GET and POST requests, and processes the response results through Promise chain calls.

references

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Methods
• https://www.w3schools.com/tags/ref_httpmethods.asp
• https://stackoverflow.com/questions/3477333/what-is-the-difference-between-post-and-get