如何将数据从JSONP转换为JSON

Question

I'm using an API that returns a JSON. Unfortunately because of CORS, I'm unable to set datatype as JSON and have to use JSONP, which the API doesn't support.

From my understanding, I can convert JSONP to JSON by giving it a callback function. It's not working and I couldn't find solutions online. Any help would be appreciated for me to convert the JSONP datatype to JSON.

$(document).ready(function() {
  $.ajax({
    type:'POST',
    url:'http://api.smmry.com/&SM_API_KEY=XXXXXX&SM_URL=HTTP-URL',
    crossDomain: true,
    dataType: 'jsonp',
    jsonpCallback: 'jsonpFunc',
    jsonp:'callback'

  });

});

function jsonpFunc(data){
  console.log(data);
};

Error I'm getting

Uncaught SyntaxError: Unexpected token :

Answer 1

The simplest way to do this is to use a server-side proxy on your server. You do not run into CORS issues with this model.

A simple example C# proxy might be:

using System;
using System.Web.UI;
using System.Net;
using System.Configuration;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        ProcessRequest(this.Page);
    }

    public void ProcessRequest(Page context)
    {
        WebClient client = new WebClient();
        string BaseUrl = ConfigurationManager.AppSettings["PassthroughTargetURL"];
        string _url = BaseUrl;
        context.Response.AddHeader("Content-type","application/json");
        string _out = client.DownloadString(_url);
        context.Response.Write(_out);
    }
}

with a calling ASPX page as follows;

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Passthrough-proxy.aspx.cs" Inherits="_Default" %>

And a config entry for the remote URL, like so:

<add key="PassthroughTargetURL" value="http://api.smmry.com/&SM_API_KEY=XXXXXX&SM_URL=HTTP-URL"/>

Assuming the URL you are calling is constant, you should get the expected result, but via your proxy - which is local to your server, so JSON will work as expected.

Your code would then become something like:

$(document).ready(function() {
  $.ajax({
    type:'POST',
    url:'http://your.server/proxy.aspx',
    dataType: 'json'
  });
});