Let me explain the problem to you a little, I'm using a 3rd party plugin that runs a rest interface for executing database commands over a postgrest database. In order to limit the returned results so I don't call all 1,000 rows is to set the request header.
This is the plugins information on this:
Limiting
PostgREST uses HTTP range headers for limiting and describing the size of results. Every response contains the current range and total results:
Range-Unit: items
Content-Range → 0-14/15
This means items zero through fourteen are returned out of a total of fifteen -- i.e. all of them. This information is available in every response and can help you render pagination controls on the client. This is a RFC7233-compliant solution that keeps the response JSON cleaner.
To request limits and offsets translate into ranges and then set the request headers
Range-Unit: items
Range: 0-4
You can also use open-ended ranges for an offset with no limit: Range: 10-.
I'm writing my own java-script library to handle the rest calls for my project. thus, I'm trying to test limiting the results to just one row returned. However I get the following console error:
Uncaught InvalidStateError: Failed to execute 'setRequestHeader' on 'XMLHttpRequest': The object's state must be OPENED.
Here is my code: note: I am going to add another var so when you make the call to get results you can set the limit programmable just trying to get it to work right now.
(function(window){
function defineCynergi(){
var Cynergi = {};
Cynergi.get = function(url){
var request = makeHttpObject();
request.open("GET", url, false);
request.setRequestHeader('Range-Unit', 'items');
request.setRequestHeader('Range', '0-1');
request.send(null);
return JSON.parse(request.responseText);
}
Cynergi.delete = function(url){
var request = new XMLHttpRequest();
request.open("DELETE", url, false);
request.setRequestHeader('Accept', 'application/:3000+json; version=1');
request.send();
deleteStatus = request.statusText;
return deleteStatus;
}
Cynergi.insert = function(url, data){
var request = new XMLHttpRequest();
request.open("POST", url, false);
request.setRequestHeader('Accept', 'application/:3000+json; version=1');
request.send(JSON.stringify(data));
sentStatus = request.statusText;
return sentStatus;
}
Cynergi.update = function(url, data){
var request = new XMLHttpRequest();
request.open("PATCH", url, false);
request.setRequestHeader('Accept', 'application/:3000+json; version=1');
request.send(JSON.stringify(data));
updateStatus = request.statusText;
return updateStatus;
}
return Cynergi;
}
if(typeof(Cynergi) === 'undefined'){
window.Cynergi = defineCynergi();
}
})(window);
function makeHttpObject() {
try {return new XMLHttpRequest();}
catch (error) {}
try {return new ActiveXObject("Msxml2.XMLHTTP");}
catch (error) {}
try {return new ActiveXObject("Microsoft.XMLHTTP");}
catch (error) {}
throw new Error("Could not create HTTP request object.");
}
and yes I know it would've been easier to use jquery, however for what i'm doing jquery doesn't work because of its precheck pass it sends to make sure the post is safe to go through isn't compatible with my plugin. This code is very early alpha stages but I've developed a pure js social media site in about 15 hours. I just get stuck on these little things because my lack of js knowledge. I also know that it would be better to set them up as asynchronous but I can't figure that out for the life of me although I've read count less post I can't seem to wrap my mind around it.
Related
I used ajax to send the data. I was successful in implementing it using two different approaches:
1) Using method 'POST' and sending data in send() method by setting requestheader.
var xmlHttp = getXMLHttpRequest();
var url="login.do";
xmlHttp.open("POST", url, true);
xmlHttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xmlHttp.onreadystatechange = function() {
if(xmlHttp.readyState == 4) {
// Done. Do nothing.
}
}
xmlHttp.send("userName=xyz&password=abc");
2) Using method "POST" and appending parameter values in the URL as:
var xmlHttp = getXMLHttpRequest();
var url="login.do?userName=xyz&password=abc";
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = function() {
if(xmlHttp.readyState == 4) {
// Done. Do nothing.
}
}
xmlHttp.send();
Since this is an ajax call, URL will not be visible in the browser window, so I wanted to know which approach is better and why?
Thanks in advance
Here is W3 recommendation for you.
That pretty much says what exactly you need to do.
Authors of services which use the HTTP protocol SHOULD NOT use GET based forms for the submission of sensitive data, because this will cause this data to be encoded in the Request-URI. Many existing servers, proxies, and user agents will log the request URI in some place where it might be visible to third parties. Servers can use POST-based form submission instead.
Though it is saying post, internal meaning of it is to keep the URL clean.
Apart from the given two ways, if I were you, I prefer clean codes (imagine 10 query param).
var data = new FormData();
data.append('userName', 'xyz');
data.append('password', 'abc');
var xmlHttp = getXMLHttpRequest();
var url="login.do";
xmlHttp.open("POST", url, true);
xmlHttp.onreadystatechange = function() {
if(xmlHttp.readyState == 4) {
// Done. Do nothing.
}
}
xmlHttp.send(data);
Putting data into the URL's query parameters doesn't make it a GET request. A POST request is a POST request; the difference is between sending data in the URL or sending it as POST body. There's no fundamental difference between both in this case, the data is equally (non) visible for anyone who cares to look.
The only arguable difference in security is that the URL will likely be logged by the server and/or proxies, while body data usually isn't. But then again, you're already sending the data to the server you presumably trust, so even that doesn't make much of a difference. And the server(s) could be logging the body as well if they wanted to.
Semantically I'd send the data in the POST body, but that's not because of security.
I think I ran into a problem of the same variable being used, I might have gotten lucky in some cases where they were separated by function scope. I recently replaced all of my jQuery code with plain JS and this broke a few things however the gained speed/lack of dependency(extra file to download) was good for me in this situation.
So I have the basic form of:
var http = new XMLHttpRequest(),
url = "php/my-script.php",
params = encodeURI('some-param='+value);
http.open("POST", url, true);
//Send the proper header information along with the request
http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http.onreadystatechange = function(data) {
//Call a function when the state changes.
if(http.readyState == 4 && http.status == 200) {
var result = JSON.parse(http.responseText);
if (result['status'] === "success") {
someFunction(result['some_key']);
}
}
}
http.send(params);
When I ran into the problem of the same http variable being used, I started to replace new ones with http1, http2, etc... seems like a bad idea. Especially having to replace all the http-method(?) calls afterwards like http2.responseText, etc... Should I make this into a function... then pass in the values to post and return the data out?
I guess I don't understand what happens when you call:
var http = new XMLHttpRequest();
Is that a one time use case, where after it has been called you need a new one for another post?
I will try the single-global-function approach. Everywhere I needed to do an AJAX call whether get or post, I always just used $.post/$.get on the spot, not sure if that's bad.
I have created a mobile application that scans the surrounding Bluetooth devices and I am able to put the devices into an array list.
Now, using the http POST method, I have to send a JSONObject having this array list to a url and even for this I have written an expected code on the android app(I am sure this code will work because I have already worked on this using POST method to URL's and displaying the response on the activity).
But, how to listen the JSONObject, sent by any android app to the URL, parse it and show it on that particular URL's webpage ?
(In short I am looking for a Javascript code which can handle this and show the list.)
if you already have the URL where the JSON is being posted to you can do:
plain js:
var request = new XMLHttpRequest();
request.open('GET', 'URL', true);
request.onload = function() {
if (request.status >= 200 && request.status < 400) {
// Success!
var data = JSON.parse(request.responseText);
} else {
// We reached our target server, but it returned an error
}
};
request.onerror = function() {
// There was a connection error of some sort
};
request.send();
with jquery:
var getData = $.getJSON('URL');
getData.done(function(data){
// you have access to data here
});
I am trying to get binary data of an image from another domain with an AJAX request. I tried various methods, but there was no working solution. I found some code on the internet that looked good, but even with this calls I get errors.
What do I wrong? Is there a standardized way to do this?
Here is what I tried until now:
var request = this.createCORSRequest('GET', 'http://url/to/image.png');
request.onload = function () {
var text = request.response;
};
request.onerror = function (error) {
alert('Woops, there was an error making the request.');
};
request.send();
private createCORSRequest(method, url) {
var xhr: XMLHttpRequest = new XMLHttpRequest();
if ("withCredentials" in xhr) {
// Check if the XMLHttpRequest object has a "withCredentials" property.
// "withCredentials" only exists on XMLHTTPRequest2 objects.
xhr.open(method, url, true);
} else if (typeof XDomainRequest != "undefined") {
// Otherwise, check if XDomainRequest.
// XDomainRequest only exists in IE, and is IE's way of making CORS requests.
var xdhr = new XDomainRequest();
xdhr.open(method, url);
} else {
// Otherwise, CORS is not supported by the browser.
xhr = null;
}
return xhr;
}
I even found this solution without ajax here on stackoverflow, but it does not work for me:
Asynchronously load images with jQuery
Here a screen of the properties the error event contains:
My goal is to get the binary of an image from a url which I get from an atom feed . I need the binaries to copy the picture to MS SharePoint.
You cannot get data from another domain unless :
the remote server allows it using CORS
you run your browser in an unsafe mode.
Reason : otherwise site A would be able to (maliciously) read the user data from site B
You must add headers to the method to allow cross domain request.
For example, if you are trying to get data from www.example.com/main.php , then you must add headers to allow those method to be called from different domain.
I'm new in JS, and having quite hard time reading the following JS code.
The first parameter of the function is a url to a PHP script, the second is a string.
What confuses me is how to read code after the line:
self.xmlHttpReq.open('POST', strURL, true);
What happens after this? Which code should i look after this line? The script?
What happens after open?
function check_detail(strURL, pids)
{
var xmlHttpReq = false;
var self = this;
// Mozilla/Safari
if (window.XMLHttpRequest) {
self.xmlHttpReq = new XMLHttpRequest();
}
// IE
else if (window.ActiveXObject) {
self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
self.xmlHttpReq.open('POST', strURL, true);
self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
self.xmlHttpReq.onreadystatechange = function()
{
if (self.xmlHttpReq.readyState == 4)
updatepage(self.xmlHttpReq.responseText, pids);
}
self.xmlHttpReq.send(getquery(pids));
}
The key is the call to "send()", which actually launches the HTTP request. That happens, but the code then proceeds immediately without waiting for the result.
When the server responds, the browser will invoke the anonymous function set up as the "readystatechange" handler. Exactly when that happens is unpredictable; it's asynchronous, in other words.
Thus, the "updatepage()" call will happen long after the "check_detail()" function has returned.
When you make an Ajax request (which is what you are doing here) it is asynchronous, which means that you don't know exactly when it will return so you can't just wait for the return.
Instead, you set up your function so that, when the request returns, a function is kicked off to handle the response. This is the onreadystatechange piece.
So the chronology will be: first the send() will occur, which will send the result of the getquery() method up to the PHP page. When that returns, the function defined within onreadystatechange will fire, which will call updatepage() and pass it both the text that was sent back from the Ajax call, and also the pids parameter.
If you're new to JavaScript, then I'd say it's a waste of time trying to figure out what's going on here - you're learning how to use the XHR object, how to make that cross-browser, and you're learning JavaScript at the same time.
I'd recommend doing the Ajax with a JavaScript library such as jQuery - don't try to learn it all now while you're learning JavaScript as well.
Most of that could be replaced with something along the lines of:
$.post(strURL, function (data) {
updatePage(data);
});
this is simple Ajax function
function check_detail(strURL, pids)
{
// definning new variable
var xmlHttpReq = false;
// creating variable self which will function as this
var self = this;
// creating HTTP request maker for Mozilla/Safari
if (window.XMLHttpRequest) {
self.xmlHttpReq = new XMLHttpRequest();
}
// creating HTTP request maker in IE
else if (window.ActiveXObject) {
self.xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
}
// so this is the confusing part right ?
// xmlHttpReq.open opens connection tu the strURL and infomation sending method
// will be POST method ( other passible values can be GET method or even else )
self.xmlHttpReq.open('POST', strURL, true);
// this defines HTTP request header (small information about what we are sending)
// in fact this is sending Content-type of information
self.xmlHttpReq.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
// when HTTP request maker state will be changed for example:
// the data will be sent or data will be received this function will be fired
self.xmlHttpReq.onreadystatechange = function()
{
// readyState 4 means data has been received
if (self.xmlHttpReq.readyState == 4)
updatepage(self.xmlHttpReq.responseText, pids); // updatepage is user defined function
}
// this actually sends the HTTP request which is made above
// but don't be confused because of this code ordering
// I mean the function defining what to do when content will be received is implemented
// before sending HTTP request right ?
// thats because if the data is too small and internet is really fast HTTP query can be
// executed faster then defining new function which will cause javascript error
self.xmlHttpReq.send(getquery(pids));
}
hope this helps
if not
more about ajax: http://en.wikipedia.org/wiki/Ajax_(programming)