Bruno Bruno - 3 years ago 174
Javascript Question

Using gettext with Javascript from PHP via XMLHttpRequest

I have an application mainly written in PHP. The translations are done using gettext().

There is a small JavaScript part which also contains strings to be translated.
I wrote this simple but working method using XMLHttpRequest:

function gettext(string_to_translate) {
var filename = get_php_script_folder() + 'gettext.php?string_to_translate=' + string_to_translate;
var xmlhttp = new XMLHttpRequest();
xmlhttp.open("GET", filename, false);
xmlhttp.send();
if (xmlhttp.status === 200) {
var translated_string = xmlhttp.responseText;
return translated_string;
} else {
console.log("Error while translating " + string_to_translate + " Status " + xmlhttp.status);
return string_to_translate; //Just give the original string.
}

}


The php file is also quite simple:

require_once '../../default.php'; //configures gettext, session management, etc.
//TODO: support for ngettext might be added.
$string_to_translate = filter_input(INPUT_GET, 'string_to_translate', FILTER_SANITIZE_STRING);
$translated_string = gettext($string_to_translate);
echo $translated_string;


In the JavaScript I just call:

var input_box_form_default_reason = gettext("Vacation");
document.getElementById('input_box_form_reason').value = input_box_form_default_reason;


If I call this function synchronously [xmlhttp.open("GET", filename, false);] Firefox/Chrome warns me that:

[Deprecation] Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.


So while this method works, it may cease to do so at any time.

But if I run the code async [xmlhttp.open("GET", filename, true);], then the next line will be executed before the result is there. The value will be undefined.

Is it feasable to make async XMLHttpRequest work in this context? Should I stick to synchronously fetching the values until some clever API is written?
Should I write my JS files with PHP? (I hope not.)

PS:


  1. I do not use any framework like jQuery. That is a "religious" thing. I want to fully understand and maintain the whole codebase myself.

  2. I read the following questions, which did not answer mine:



Answer Source

Yes, you need a callback!

function gettext(string_to_translate, obj, callback)
... //your original xmlhttprequest
xmlhttp.callback = callback;, add a callback to the xmlhttp

//set the readystate event that listens to changes in the ajax call
xmlhttp.onreadystatechange = function()
{
    //target found and request complete
    if (this.status === 200 && this.readyState == 4) {
        //send result to the callback function
        this.callback(obj, this.responseText);
    } else {
        console.log("Error while translating " + string_to_translate + " Status " + xmlhttp.status);
        this.callback(obj, string_to_translate);
    }
}

//callback function specific for this case.
function setValue(obj, value)
{
   obj.value = value;
}

To call this:

gettext("Vacation", document.getElementById('input_box_form_reason'), setValue);

An extended ajax function with callback

function ajax(url, method, json, callBack)
{
	//it supports get and post
	//returns parsed JSON, when json is set to true. | json accessible via this.JSON in the callBack
	//a callback can be attached where the this refers to the xmlHTTP
	//supply an url like you would in a get request: http://www.example.com/page.php?query=1
	//start the request with xmlDoc.fire.
	
	var xmlDoc = new XMLHttpRequest
	xmlDoc.JSON = json ? true : false;
	xmlDoc.error = true;
	xmlDoc.errorMessage = "";	
	xmlDoc.errorObj = {"error" : xmlDoc.error, "object" : "XMLHttpRequest", "message" : xmlDoc.errorMessage, "url" : url, "sync" : true, "method" : (method ? "POST" : "GET")};
	xmlDoc.url = url
	xmlDoc.method = method ? "post" : "get";
	
	xmlDoc.preserveWhiteSpace = true;

	if (method == "post")
	{
		xmlDoc.pUrl = url; 
		xmlDoc.pArg = "";
		if (url.match(/\?/)) //we need to filter out the arguments since the are send seperately. 
		{
			var splitted = url.split(/\?/);
			xmlDoc.pUrl = splitted[0];
			xmlDoc.pArg = "";
			for (var i = 1; i < splitted.length; i++)
			{
				xmlDoc.pArg += splitted[i];	//prevent additional questionmarks from being splitted.				
			}					
			
		}
		
		xmlDoc.open.apply(xmlDoc, ["post", xmlDoc.pUrl , true]); //set up the connection
		
		xmlDoc.setRequestHeader("Content-type", "application/x-www-form-urlencoded ; charset=UTF-8");
	}
	else
	{
		//get request, no special action need, just pass the url
		this.xmlDoc.open("get", url, true); //true for async
	}

	xmlDoc.onreadystatechange = readyStateXML.bind(xmlDoc, callBack);
	xmlDoc.setRequestHeader("Pragma", "no-cache");
	xmlDoc.setRequestHeader("Cache-Control", "no-cache, must-revalidate");
	
	xmlDoc.fire = fireXmlRequest; //set up fire function.
	
	return xmlDoc;
}

function fireXmlRequest()
{
	if (this.method == "post")
	{
		this.send(this.pArg); //post
	}
	else
	{
		this.send(null); //get
	}
}

function readyStateXML(callBack)
{
	if (this.readyState == 4)
	{
		//request completed, now check the returned data
		//We always assume that a request fails.
		if (this.errorMessage == "XML Not loaded." || this.errorMessage == "")
		{
			this.error = false; //set error to false, request succeeded.
			this.errorObj.error = false;			

			if (!this.responseXML && !this.JSON)
			{
				this.error = true;
				this.errorMessage = "invalid XML.";
				this.errorObj.error = this.error;
				this.errorObj.message = this.errorMessage;				
			}
			
			if (this.error == false)
			{
				this.xmlData = this.responseXML;
				
				if (this.JSON)
				{
					try
					{
						this.JSON = JSON.parse(this.responseText);
					}
					catch(err)
					{
						//JSON couldn't be parsed
						this.error = true;
						this.errorMessage = err.message + "<br />" + this.responseText;
						this.errorObj.error = this.error;
						this.errorObj.message = this.errorMessage;		
					}
				}
				
			}
			
			//404 or 400, not found error
			if (this.status == "400" || this.status == "404" || this.status == 400 || this.status == 404)
			{
				this.error = true;
				this.errorMessage = "404: The requested page isn't found.";
				this.errorObj.error = this.error;
				this.errorObj.message = this.errorMessage;				
			}
			else if(this.status == "500")
			{
				this.error = true;
				this.errorMessage = "500: Internal server error.";
				this.errorObj.error = this.error;
				this.errorObj.message = this.errorMessage;				
			}

			if (typeof(callBack) != "undefined")
			{
				callBack.call(this); //pass the xmlDoc object to the callBack
			}
		}
		else
		{
			alert("Error \n" + this.errorMessage);
			if (typeof(callBack) != "undefined")
			{
				callBack.call(this);
			}
		}
			
	}
	else
	{
		this.error = true;
		this.errorMessage = "XML Not loaded.";
		this.errorObj.error = this.error;
		this.errorObj.message = this.errorMessage;		
	}
}

//to use
ajx = ajax("index.php?query=1", "post", true, false, function(){/*callback*/});
   console.log(ajx);
   ajx.fire();

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