Know res.send() and res.end() of Express

know Express Of res.send() and res.end()

Preface

In the use of Node.js In the server code of , If you are using Express frame , So for a request , There are often two ways to respond ：

//  Method 1
app.get("/end", (req, res, next) =>{
    res.end(xxx);
});
//  Method 2
app.get("/send", (req, res, next) =>{
    res.send(xxx);
});

So what's the difference between the two methods ？ What are their application scenarios ？ This is what I need to make clear today .

Express And res.end()

Definition

It can quickly end the response without any data .

This method actually comes from Node The core , Specifically http.ServerResponse.Use Of response.end() Method ：

image-20220121021236372

grammar

res.end([data[, encoding]][, callback])

Argument parsing ：

• data <string> | <Buffer>
• encoding <string>
• callback <Function>

thorough

If res.end() Method passes in an object , There will be an error ：

image-20220121012102733

Express And res.send()

Definition

Send... To the requesting client HTTP The response message .

grammar

res.send([body[,statusCode]])

body Parameters can be Buffer、Object、String、Boolean or Array.

thorough

Through code debugging , We can find out ,Express Of res.send() The method finally calls http.ServerResponse.Use Of response.end() Method ：

// node_modules/express/lib/response.js
res.send = function send(body) {
  var chunk = body;
  var encoding;
  ……
  if (req.method === 'HEAD') {
    // skip body for HEAD
    this.end();
  } else {
    // respond
    this.end(chunk, encoding);
  }
  return this;
};

contrast

The same thing

Express Of res.end() and res.send() Similarities of methods ：

1. Both eventually return to http.ServerResponse.Use Of response.end() Method .
2. Both will end the current response process .

Difference

Express Of res.end() and res.send() The difference in approach ：

1. The former can only send string perhaps Buffer type , The latter can send any type of data .
2. Semantically speaking , The former is more suitable for scenarios without any response data , The latter is more suitable for scenarios with response data .

summary

Express Of res.end() and res.send() Method usage , It is generally recommended to use res.send() The method can , This eliminates the need to care about the format of the response data , because Express The data is processed internally .

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