Develop Reference

Custom attr() method cannot be given a different name

I have the following perfectly working code (written by someone else). The problem is that if I simply rename the attr method, I get an error. For example, I rename the method to attrx and get this error:
TypeError: arg.attrx is not a function
Here is the working code:
function Action(name) {
this.attr = function(n) {
if (n=="name") {
return "action";
}
},
this.val = function() {
return name;
};
}
Action.prototype.toString = function() {
return "&" + this.attr("name") + "=" + this.val();
}
When a user triggers an event, the following function is called:
function serializeElements() {
var result = "";
for(var i = 0; i < arguments.length; i++) {
var arg = arguments[i];
result += (arg.attr("name") + "=" + arg.val() + "&");
}
return result;
}
Here is the identical code above but it has the attr method renamed to attrx:
function Action(name) {
this.attrx = function(n) {
if (n=="name") {
return "action";
}
},
this.val = function() {
return name;
};
}
Action.prototype.toString = function() {
return "&" + this.attrx("name") + "=" + this.val();
}
function serializeElements() {
var result = "";
for(var i = 0; i < arguments.length; i++) {
var arg = arguments[i];
result += (arg.attrx("name") + "=" + arg.val() + "&");
}
return result;
}
I cannot figure out the reason that the code does not work (see error at top of message) after I rename the method to attrx or anything else for that matter.
Note: The web page does include jQuery, but I don't think that is what causes the problem.
Here is the code used to call serializeElements:
function addStatesListener() {
$("#states").on("change", function(e) {
var form = $(this.form);
var url = form.attr("action");
var type = form.attr("method");
// pass 1) jQuery 'country' and 'state' objects and 2) a query string fragment, e.g.: '&action=change_state'
var data = serializeElements($("#countries"), $("#states"), new Action("change_state"));
e.preventDefault();
$.ajax({
url: url,
type: type,
data: data,
dataType: "html", // The type of data that you're expecting back from the server
success: function(result) {
$("#cities").html(result); // list of all cities, e.g.: <option value="Albany"</option>
}
});
});
}

The proper answer to your question is want already catch #dinesh, you are passing 3 arguments to your function, and only the third is an Action with the .attrx method you changed.
Considering you are working on jquery objects, and if you want to clean your code, you could use .serialize() method instead of calling the couple .attr() and .val().
.serialize() is the jquery method to serialize form objects.
So you can change your code as follow:
function Action(name) {
this.serialize=function() {
return 'name='+encodeURI(name);
}
}
And then your function serializeElements:
function serializeElements() {
var args = Array.prototype.slice.call(arguments);
return args.reduce(function(a, b){
if (a) return a.serialize() + '&' + b.serialize();
if (b) return b.serialize();
});
}
Then you can call it so:
var data = serializeElements($("#countries,#states"), new Action("change_state"));
As you see, you could put form elements in a comma separated list on jquery selector.
That's it.

Parsing arguments to functions involving ajax

I am having an issue trying to improve the functionality of my ajax functions by adding arguments to define what to do with the returned result.
So what i am trying to implement is a way to tell the function to append the result to a given element by its id. But i am having difficulty understanding how to add this functionality.
This is my current code:
var ajax = new function(){
var self = this;
self.x = function() {
if (typeof XMLHttpRequest !== 'undefined') {
return new XMLHttpRequest();
}
};
self.send = function(url, callback, method, data, sync) {
var x = self.x();
x.open(method, url, sync);
x.onreadystatechange = function() {
if (x.readyState == 4) {
callback(x.responseText)
}
};
if (method == 'POST') {
x.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
}
x.send(data)
};
self.get = function(url, data, callback, sync) {
var query = [];
for (var key in data) {
query.push(encodeURIComponent(key) + '=' + encodeURIComponent(data[key]));
}
self.send(url + (query.length ? '?' + query.join('&') : ''), callback, 'GET', null, sync)
};
};
I then make an ajax request like so:
//get the html file, and then call a function
ajax.get(dir.layout+'login.html',false,
function(){
elements.addTemplate(data,'parent',true);
});
In Chrome the xhr shows the correct data and contents, so i know that part works. In my elements.loadTemplate function i have these three lines with their actual values:
elements.addtemplate(data,div_id,append){
console.log(data); //shows:
console.log(div_id); //shows string: parent
console.log(append); //shows: true
}
Now the issue is data is blank, when i want it to contain the contents of the HTML file that I just requested (in this case login.html). I am wondering why it would show up as blank and how i can fix it?

your data is undefined because your callback doesn't accept a parameter
try this:
ajax.get(dir.layout+'login.html',false,
function(data){ // <=== data
elements.addTemplate(data,'parent',true);
});

Identify the caller (or how pass parameter) of a callback (JSON) function in JavaScript

When i request
BASE_URL + 'json/valueone?callback=fnCallBack0'
the response from server is treated in a callback function. This function receives (ASYNCHRONOUS) data (JSON format) but do not include the initial parameter "valueone"
var BASE_URL = ...
function fnCallBack(data){
if (data != null) {
// HERE...I NEED ID <====================
// arguments.callee.caller <==================== dont work
console.log('information', data);
}
}
// onclick callback function.
function OnClick(info, tab) {
var arrH = ['valueone', 'valuetwo'];
arrH.forEach(function(value) {
var scrCallBack = document.createElement('script');
scrCallBack.src = BASE_URL + 'json/' + value + '?callback=fnCallBack';
//BASE_URL + 'json/one?callback=fnCallBack0';
document.body.appendChild(scrCallBack);
});
My solution is to create an intermediate function correlative name (fnCallBack0, fnCallBack1, ...), a global array, and a counter. Works fine, but this is not OOP, is a fudge.
var BASE_URL = ...
//global array
var arrH = [];
var fnCallBack0 = function(data){
fnCallBack(data, '0');
}
var fnCallBack1 = function(data){
fnCallBack(data, '1');
}
function fnCallBack(data, id){
if (data != null) {
console.log('information', data + arrH[id]);
}
}
// onclick callback function.
function OnClick(info, tab) {
var i = 0;
arrH = ['valueone', 'valuetwo'];
arrH.forEach(function(value) {
var scrCallBack = document.createElement('script');
scrCallBack.src = BASE_URL + 'json/' + value + '?callback=fnCallBack' + (i++).toString();
//BASE_URL + 'json/one?callback=fnCallBack0';
document.body.appendChild(scrCallBack);
});
chrome.contextMenus.create({
title: '%s',
contexts: ["selection"],
onclick: function(info) {console.log(info.selectionText)}
});
var idConsole = chrome.contextMenus.create({
title: 'console',
contexts: ["selection"],
onclick: OnClick
});
I tried with inject function as code in html page, but i receeived "inline security error", and a lot of similar questions.
Please, NO AJAX and no jQuery.
This is my first post and my first chrome extension
Thanks in advanced.

I don't see how anything of this has to do with OOP, but a solution would be to just create the callback function dynamically so that you can use a closure to pass the correct data:
function fnCallBack(data, value){
if (data != null) {
console.log('information', data + value);
}
}
// onclick callback function.
function OnClick(info, tab) {
['valueone', 'valuetwo'].forEach(function(value, index) {
// unique function name
var functionName = 'fnCallback' + index + Date.now();
window[functionName] = function(data) {
fnCallBack(data, value);
delete window[functionName]; // clean up
};
var scrCallBack = document.createElement('script');
scrCallBack.src = BASE_URL + 'json/' + value + '?callback=' + functionName;
document.body.appendChild(scrCallBack);
});
}

Node file uploads and sychronicity

While I'm generally comfortable with rudimentary asynch patterns in node I have come across a situation where I need the return value from an asynch call in a generally synchronous situation.
Given the function:
modelHelper.saveFile = function(field) {
var url = cloudinary.uploader.upload(this.req.files[field.name].path, function(result) {
if(typeof result.url != "undefined" && result.url.length > 0)
{
console.log(" \n\n\n Inside the cloudinary call.");
console.log("\n\n URL = " + result.url);
return result.url;
}
return false;
});
console.log("\n\n\n Outside the load, URL =" + url);
if(!url) return "";
return url;
};
This function is called in the case of uploading a file to a server, and is called by a simple loop which loops over all of the elements of a page. For the majority of cases it's a simple mapping of variable to value, as such I really don't want to need to inject a next into this function.
Here's the caller:
modelHelper.parseField = function(field) {
var type = field.type;
switch(type) {
case "email":
case "url":
return strings.exists(this.param(field.name)) ?
this.param(field.name) : "";
break;
case "file":
return modelHelper.resolveFile.bind(this)(field);
break;
default:
return strings.exists(this.param(field.name)) ?
strings.makeSafe(this.param(field.name)) : "";
}
and this, in turn is called by:
modelHelper.populate = function(elements, record, next){
var len = elements.length;
parseField = modelHelper.parseField.bind(this);
while(len--)
if((elements[len]["type"] != "captcha"))
this[record][elements[len]['name']] = parseField(elements[len]);
next.bind(this)();
};
as such, I'm looking for a pattern that will block execution until the file operation in saveFile returns a variable; something like wrapping it in a setInterval type call was my first thought, but is there a better way?

Pass a callback to saveFile and call it with the url once the upload is complete
modelHelper.saveFile = function(field, callback) {
var url = cloudinary.uploader.upload(this.req.files[field.name].path, function(result) {
if(typeof result.url != "undefined" && result.url.length > 0) {
console.log(" \n\n\n Inside the cloudinary call.");
console.log("\n\n URL = " + result.url);
return callback(null, result.url);
}
return callback();
});
};

Using My Own Callback with an HttpRequest Object

I'm writing an Http Request without the use of a library (another script was having conflits...)
But Im having trouble with the scope of my object. Below is the calling script, then the Ajax_Request object follows.
function loadCard(e) {
var element = e.target;
if($('overlay')) {
return false; //something is already over the layout
}
var card = '/card/'+element.id;
var option = {method:'post', parameters:'test', async:true}
loadOverlay();
var ajax = new Ajax_Request(card, option);
}
//Ajax_Request
function Ajax_Request(url, options) {
if(typeof url !== 'undefined') {
this.url = url;
}
if(typeof options.method !== 'undefined') {
this.method = options.method;
} else {
this.method = 'get';
}
if(typeof options.parameters !== 'undefined') {
this.parameters = options.parameters;
}
if(typeof options.async !== 'undefined') {
this.async = true;
} else {
this.async = false;
}
if(window.XMLHttpRequest) {
this.request = new XMLHttpRequest();
} //check for MS browser
this.makeRequest = function() {
try {
this.request.onreadystatechange = this.checkReadyState;
this.request.open(this.method, this.url, this.async);
if(this.method == 'post') {
this.request.send(this.parameters);
} else {
this.request.send(null);
}
} catch(err) {
alert(err);
}
}
this.setResponse = function(r) {
alert(r)
this.response = r;
}
this.getResponse = function() {
return this.responseText;
}
this.checkReadyState = function(r) {
switch(this.readyState) {
case 4:
//Represents a "loaded" state in which the response has been completely received.
if(this.status == 200) {
this.setResponse(this.responseText)
}
...
}
}
}
I'm trying to set the response to a property so my calling object can work with it.
But when I try to call this.setResponse(), I get an error that it's undefined.
How can I tie the onreadystatechange callback to my program properly?
The script otherwise returns the data properly, and I could simply output it right there, but I need a bit more flexibility.
Thanks
Rich

This is happening to you because inside the checkReadyState function this actually represents the XMLHttPRequest instance not you Ajax_Request object, thus this.setResponse is undefined. In order to reference your object´s method you have to use a little trick: var that = this.
function Ajax_Request(url, options) {
var that = this;
...
this.checkReadyState = function (r) {
switch(this.readyState) {
case 4:
if(this.status == 200) {
// "this" refers to the XMLHttpRequest,
// but "that" refers your custom Ajax object
that.setResponse(this.responseText)
}
...
}
}
}

I'm not sure whether this is the problem, but you shouldn't be referring to Ajax_Request within the constructor. Use this instead. (this refers to the actual object instance—Ajax_Request refers to the object constructor.)
this.makeRequest = function() {
try {
this.request.onreadystatechange = this.checkReadyState;
this.request.open(this.method, this.url, this.async);
if(this.method == 'post') {
this.request.send(this.parameters);
} else {
this.request.send(null);
}
} catch(err) {
alert(err);
}
};

In this.checkReadyState, try changing this.setResponse(this.responseText) to this.setResponse(this.request.responseText);.