Express get request

For yourself Express Of Get request

Last article yes Express Of Hello World. Here we'll see how to Express In dealing with Get request .

General operation

General operation , I haven't mentioned it since last time request Start with the object （ The following content has deleted about cookie The department in charge of the , I hope I have the opportunity to study cookie Well ）.

app.get('/index', function (req, res) {
    
  console.log(JSON.stringify(req.app === app, null, 2)); // true
  console.log(`req.baseUrl: ${
      req.baseUrl}`); //  empty , Related to routing 
  console.log(`req.hostname: ${
      req.hostname}`);  
  // 192.168.1.5 | localhost
  console.log(`req.ip: ${
      req.ip}`);  
  // ::ffff:192.168.1.5 | ::1
  console.log(`req.ips: ${
      req.ips}`);  //  empty 
  console.log(`req.method: ${
      req.method}`); // GET
  console.log(`req.originalUrl: ${
      req.originalUrl}`); // /index
  console.log(`req.params: ${
      JSON.stringify(req.params || [], null, 2)}`);
  console.log(`req.path: ${
      req.path}`); // /index
  console.log(`req.protocol: ${
      req.protocol}`); // http
  console.log(`req.query: ${
      JSON.stringify(req.query || [], null, 2)}`); 
  // { "username": "tom", "password": "jerry" }
  console.log(`req.route: ${
      JSON.stringify(req.route || [], null, 2)}`);
  console.log(`req.secure: ${
      req.secure}`); // false
  console.log(`req.subdomains: ${
      req.subdomains}`);
  console.log(`req.xhr: ${
      req.xhr}`); // false
  res.end();
});

First of all, I would like to introduce about ip and hostname Content , Because I was a little confused when I saw it for the first time

monitor host	ip	hostname
Default	::1	localhost
127.0.0.1	127.0.0.1	localhost
192.168.1.5( Connect WiFi Time machine IP)	::ffff:192.168.1.5	192.168.1.5

Refer to the Information and Node Official website Description of , Just know the following content .
IPv6 It's made up of two parts ： Subnet prefix and Interface suffix .IPv6 altogether 128bit, These two parts are 64bit. If IPv4 The address is embedded in IPv6 in , To make any IPv6 The parser knows that it is processing a IPv4 The address of , So add... To the front Subnet prefix . Subnet prefix Continuous in 0 It can be omitted , therefore ::ffff: It's actually 0000:0000:ffff:0000.
that ::1 Empathy , yes IPv6 Of localhost An abbreviated version of , The full version should be 0:0:0:0:0:0:0:1.

obtain Get Request parameters

Use request.query obtain URL Parameters

app.get('/getUser', (req, res) => {
    
  res.send(JSON.stringify(req.query));
});

If you want to get these variables , have access to Deconstruct assignment grammar , Or directly . Get the variables

app.get('/getUser', (req, res) => {
    
  let {
     name } = req.query; // tom
  let age = req.query.age; // 12
  let address = req.query.address; // undefined
  console.log(name, age, address);
  res.send(req.query);
});

Actually , I used to be curious , If you want to pass an object or array in a parameter, you can only use POST request , Until I saw express Documents —— use GET No problem ！ But they all need to use [] Operator
First, arrays , Just use Array name []= Parameter values

// http://localhost:3000/getUser?users[]=tom&users[]=jerry&users[]=dog
app.get('/getList', (req, res) => {
    
  let users = req.query.users
  res.end(users);
});

Then the object , need Object name [ Property name ]= Property value

// http://localhost:3000/getUser?tom[name]=tom&tom[age]=12&tom[address]=house
app.get('/tom', (req, res) => {
    
  let tom = req.query.tom;
  res.end(tom);
});

obtain Get Path parameter

be familiar with Springboot We all know that we can define parameters in the route , And then use @PathVariable Annotation gets the parameter , stay express No problem in . We need to use : Parameter name Defining parameters

app.get('/user/:id', (req, res) => {
    
  console.log(req.params.id);
  res.end(req.params.id);
});

Of course , We can define more than one parameter

app.get('/image/:width/:height', (req, res) => {
    
  console.log(req.params.width);
  console.log(req.params.height);
  res.end(JSON.stringify(req.params));
});

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