编辑：无法使用 Fetch API 向 Express 服务器发送 POST 请求，不断收到 JSON.parse 错误

Question

I'm new to JavaScript, and am learning to develop with an Express server on Glitch.com. I am running into issues with my Fetch API POST request, where it keeps returning a JSON.parse error when I try to send it a JSON object.

SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

I plan on using the JSON object to take in input from an HTML form, and I have that data saved in string variables but cannot use it. When I test JSON.stringify and JSON.parse in the console, it logs it as

Object { some: 1 }

I am also not sure where I should be directing the URL of the Fetch API, though the Express code is saved in a folder in Glitch called "server/ex.js". Thank you in advance!

UPDATE So it looks like I'm getting errors with my Express server, when I check the response status code it's 404. How do I find the right URL?

Answer 1

try this code:

var payload = {
    a: 1,
    b: 2
};

var data = new FormData();
data.append( "json", JSON.stringify( payload ) );

fetch("/echo/json/",
{
    method: "POST",
    body: data
})
.then(function(res){ return res.json(); })
.then(function(data){ alert( JSON.stringify( data ) ) })

This code above is in: Fetch: POST json data

Answer 2

If you started a node project, you will want to edit the server.js file to include the following codes:

app.post('/server/ex.js',function(req,res){
  res.send(JSON.stringify({
    'hello':'world'
  }))
})

then the fetch request in client.js should return the json object

edit1) sorry, just realised it was a post request, not a get request

edit2) in order to parse the json object you sent {some:1} , you will need bodyparser package .

edit after seeing server.js :

you will need the following for server.js at the very top if it does not already:

var express = require('express')
var app = express()

in addition, it will need the code snippit above somewhere later.

I am not too sure where you are getting the next() function from, though.