jsonp请求上的“ Uncaught TypeError：无法读取未定义的属性'toLowerCase'”

Question

I have a node server and an application from another server doing a AJAX jsonp request via jquery to get a json array of parameters, but when i request the data the jquery throws this error:

Uncaught TypeError: Cannot read property 'toLowerCase' of undefined 

The request is sent and i get the response, but i can't get the data in the javascript client-side

Node server:

var my_http = require('http');


var databaseUrl = "leitordecarga"; // "username:password@example.com/mydb"
var collections = ["tables"]
var db = require("mongojs").connect(databaseUrl, collections);

var callback = [];
db.tables.find(function(err,values){
    if(err || !values){
        console.log('error');
    }else{
        values.forEach(function(value){
            callback.push(value);
        });
    }
});


my_http = require("http");  
my_http.createServer(function(request,response){  
    response.writeHeader(200, {"Content-Type": "application/json"});  
    response.write(JSON.stringify(callback));  
    response.end();  
}).listen(8080); 

Javascript in client-side:

$(document).ready(function(){
    $.ajax({
        url:'http://localhost:8080/mongo.js',
        dataType:'jsonp',
        type: "GET",
        jsonp : "callback",
        contentType: "application/jsonp",
        success: function(data){
            console.log(data);
        },
        error: function(data){
            console.log(data.getResponseHeader());
        }
    }).done(function( data ) {
        console.log(data);
    });
}); 

im using jquery 2.1.0 but i've tried other versions and the error persists

My question is how i can get the data in the success clause

Answer 1

The problem in this case seems to be this line:

console.log(data.getResponseHeader());

You're not supposed to call the getResponseHeader without any parameters. The error is technically that jQuery doesn't check if the key was given as an argument before calling toLowerCase() to it, however, the actual getResponseHeader implementation also throws an error if no parameters were given.

If you meant to just return ALL the response headers, you should use:

console.log(data.getAllResponseHeaders())

Answer 2

JSONP response differs from JSON response. With JSONP you actually respond with a JavaScript code.

So you have to modify your code like this:

First, require querystring module in the top of your script:

var qs = require('querystring');

And then you have to rewrite your HTTP request handler:

my_http.createServer(function(request,response){  
    var funcName = qs.parse(request.url).callback;
    response.writeHeader(200, {"Content-Type": "text/javascript"});
    response.write(funcName + '(' + JSON.stringify(callback) + ');');
    response.end();
}).listen(8080); 

You can learn more about JSONP here