How do I send variables to the server with XMLHTTPRequest
? Would I just add them to the end of the URL of the GET
request, like ?variable1=?variable2=
, etc?
So more or less:
XMLHttpRequest("GET", "blahblah.psp?variable1=?" + var1 + "?variable2=" + var2, true)
The XMLHttpRequest method send() sends the request to the server. If the request is asynchronous (which is the default), this method returns as soon as the request is sent and the result is delivered using events. If the request is synchronous, this method doesn't return until the response has arrived.
The async parameter of the open() method should be set to true: xhttp.
setRequestHeader('Content-Type', 'application/json') ; is added 1 line above or below the Accept header, the method used changes to OPTIONS, the Accept header changes to "text/html,application/xhtml+xml,application/xml;q=0.9,/;q=0.8" and the Content-Type header disappears as if it wasn't seen.
If you want to pass variables to the server using GET that would be the way yes. Remember to escape (urlencode) them properly!
It is also possible to use POST, if you dont want your variables to be visible.
A complete sample would be:
var url = "bla.php"; var params = "somevariable=somevalue&anothervariable=anothervalue"; var http = new XMLHttpRequest(); http.open("GET", url+"?"+params, true); http.onreadystatechange = function() { if(http.readyState == 4 && http.status == 200) { alert(http.responseText); } } http.send(null);
To test this, (using PHP) you could var_dump $_GET
to see what you retrieve.
Manually formatting the query string is fine for simple situations. But it can become tedious when there are many parameters.
You could write a simple utility function that handles building the query formatting for you.
function formatParams( params ){ return "?" + Object .keys(params) .map(function(key){ return key+"="+encodeURIComponent(params[key]) }) .join("&") }
And you would use it this way to build a request.
var endpoint = "https://api.example.com/endpoint" var params = { a: 1, b: 2, c: 3 } var url = endpoint + formatParams(params) //=> "https://api.example.com/endpoint?a=1&b=2&c=3"
There are many utility functions available for manipulating URL's. If you have JQuery in your project you could give http://api.jquery.com/jquery.param/ a try.
It is similar to the above example function, but handles recursively serializing nested objects and arrays.
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