I use the fetch request parameters, using the get method can take to normally, use the delete and po-CodePudding

# # this is my js file

 
Const express=the require (' express ') 
Const app=express () 
Const bodyParser=the require (' body - parser) 
App. Use (express. Static (' public ')) 
App. Use (bodyParser. Json ()); 
App. Use (bodyParser. Urlencoded ({extended: false})) 

App. All (' * ', function (the req, res, next) {
Res. The header (" Access - Control - Allow - Origin ", "*"); 
Res. The header (" Access - Control - Allow - the Methods ", "PUT, GET, POST, DELETE, the OPTIONS"); 
Res. The header (" Access - Control - Allow - the Methods ", "X - Requested - With"); 
Res. The header (" Access - Control - Allow - the Methods ", "the content-type"); 
next(); 
}); 
//the fetch traditional way 
App. Get ('/fetchdata '(the req, res)=& gt; {
Res. The send (' traditional method to obtain parameters' + the req. Query. Id) 
}) 
//the fetch second way 
App. Get ('/fetchdata: id, (the req, res)=& gt; {
Res. The send (' 2 methods for parameters' + the req. Params. Id) 
}) 
App. Delete ('/fetchdata: id, (the req, res)=& gt; {
Res. The send (' delete method to obtain parameters' + the req. Params. Id) 
}) 
App. Post ('/fetchdata '(the req, res)=& gt; {
Res. The send (' dpost method to obtain parameters' + the req. Body. The username + "-- -- -- -- -- -- -- -- -- --" + the req. Body. The password) 
}) 
App. Get ('/a1, (the req, res)=& gt; {
SetTimeout (function () {
Res. The send (' a1) 
}, 1000); 
}) 
App. Get ('/a2, (the req, res)=& gt; {
SetTimeout (function () {
Res. The send (' a2 ') 
}, 2000); 
}) 
App. Get ('/a3, (the req, res)=& gt; {
SetTimeout (function () {
Res. The send (' a3) 
}, 3000); 
}) 
App. Get ('/data '(the req, res)=& gt; {
Res. The send (" Hello World ") 
}) 
App. Get ('/data1, (the req, res)=& gt; {
Res. The send (' Hello Tom ') 
}) 
App. Get ('/data2, (the req, res)=& gt; {
Res. The send (' Hello jerry) 
}) 
App. Listen (' 3000 ', ()=& gt; {
The console. The log (" running ") 
})

# # this is my HTML files, used to request js data, using the get method can successfully

 
 
 
<meta charset="utf-8" & gt; 
<script SRC="https://bbs.csdn.net/topics/vue.js" & gt; </script> 
 Document 
 
<body> 
<script> 
//the fetch (' http://localhost:3000/a1 '). Then (function (data) {
////this necessary, used to get the background object 
//return data. The text (); 

//}). Then (function (data) {
//the console. The log (data); 
//}) 


//the fetch the ginseng 
//the fetch (' http://localhost:3000/fetchdata? Id=156 ', {
//method: 'get' 
//}). Then (function (data) {
//return data. The text (); 
//}) 
//. Then (function (data) {
//the console. The log (data); 
//}) 
//second way (here with the get method can successfully) 
//the fetch (' http://localhost:3000/fetchdata/456 ', {
//method: 'get' 
//}). Then (function (data) {
//return data. The text (); 
//}) 
//. Then (function (data) {
//the console. The log (data); 
//}) 
//here with the delete method would have failed 
Fetch (' http://localhost:3000/fetchdata/741 '{
Method: 'delete' 
{}). Then (function (data) 
Return the data. The text (); 
}) 
Then (function (data) {
console.log(data); 
}) 
</script>

this is an error message
Failed to load Method DELETE http://localhost:3000/fetchdata/741: is not allowed by the Access - Control - Allow - the Methods in preflight response.