jquery ajax callback function without dynamic parameters - javascript

I have an array with objects, I want to save each one of them via GET, and update certain params in the callback, bot
the html:
<html><body><div id='test'><div id="a">a</div><div id="b">b</div></div></body></html>
the js:
$.map($("#test > div"), save)
save = function(o,i){
itt = $(o)
tmp = {'desc':itt.html()};
$.get('ajax/update_post', {'data':array2json(tmp)}, function(a){
alert(itt.attr('id'))
updatePostBack(a,itt)
})
}
updatePostBack = function(a,item){
alert(item.attr('id'))
}
the updatePostBack is always receiving the las item!
how can I pass the right id or object to a callback function in js / jquery?

The solution is so sadly mundane: you needed to add var in front of your variables to declare them as new. They were being overwritten inappropriately by the next iteration before the first one could complete. This code works for me:
save = function(o,i){
var itt = $(o)
var tmp = {'desc':itt.html()};
$.get('ajax/update_post', {'data':array2json(tmp)}, function(a){
alert(itt.attr('id'))
updatePostBack(a,itt)
})
}
updatePostBack = function(a,item){
alert(item.attr('id'))
}
$.map($("#test > div"), save);
I also moved the map statement to the end so that it's calling the save function after it's been declared.

Related

Accessing a JavaScript / jQuery Instance only once

I have a jQuery function which is called on several events (button click, change etc.)
This function is called in the documentReadyFunction and is feeded with start values..
everytime I call this function, parameters will be passed to the function.
My problem is: I don't want to create a new Object each time I call the function, because if I set a variable which decides if a part of the function is beeing executed or not, will be always overwritten..
What do I have to do, to access the first created instance instead of creating always a new one with every function call..
Down below is a simplyfied version of my function.. Maybe you understand my problem better then.
$.fn.doSomething = function(param1) {
var localParam = param1;
var amIcalledMoreThanOnce = parseInt(0, 10);
if (param1 == 1) {
amIcalledMoreThanOnce = amIcalledMoreThanOnce + 1;
if (amIcalledMoreThanOnce == 1) {
$('#run').val(amIcalledMoreThanOnce);
// fill form fields with URL parameters
// This shall be executed only once after getting the URL vals
} else {
// set the localParam to 0 to exit this loop and reach the outter else..
localParam = 0;
$.fn.doSomething(localParam);
}
} else {
$('#run').val(amIcalledMoreThanOnce);
// use the User Input Data not the URL Params
}
};
$.fn.doSomething(1);
$.fn.doSomething(1);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.0/jquery.min.js"></script>
<input type="number" id="run">
you can use this pattern:
var nameOfYourFunction = (function() {
var initializedOnlyOnce = {};
return function() {
//use initializedOnlyOnce here.
}
})();
here what you see is; you create and run a function immediately when the code is run. The outer function immediately returns the inner function and it's assigned to nameOfYourFunction. Then you can use the nameOfYourFunction(); just as any other function. However any varible declared in the outer function will be available to the nameOfYourFunction() and initializedOnlyOnce will never be initialized again.

Create variable to JavaScript array from another function?

I have a function that create and store an array for all the p elements:
function dummyArray(){
var $dummy= $('p');
var dummy= [];
i = 0;
$dummy.each(function()
{
dummy[i++] =$(this).html();
});
return dummy;
}
Now, in order to reuse the array in another function, I can use dummyArray() and dummyArray()[0] to access the individual data.
function initAll(){
//dummyArray();
//dummyArray()[0];
}
However I want to store it inside a variable like below but it gives me error.
function initAll(){
var allArray = dummyArray();//error
}
Is there a way to store it inside a variable or is there a better way of doing this?
After cleaning up my code I noticed that using var allArray = dummyArray(); does work, the error was generated from something else. cheers~
Edited:
The error I found out was the function name cannot be the same as the new variable name declared even though the () aren't there.
var dummyArray = dummyArray();//error
var allArray = dummyArray();//works

Variable scope in Javascript Object

I'm discovering the concept of "objects" in JavaScript. I'm making an RSS Parser, and I have an error (commented).
function MyParser (feed_url) { // Construct
"use strict";
this.feedUrl = feed_url;
this.pubArray = [];
if (typeof (this.init_ok) == 'undefined') {
MyParser.prototype.parse = function () {
"use strict";
var thisObj = this;
$.get(this.feedUrl, function (data, textStatus, jqXHR) {
if (textStatus == 'success') {
var xml = jqXHR.responseXML,
//lastBuildDate = new Date($(xml).find('lastBuildDate').text());
items = $(xml).find('item');
items.each(function () {
var pubSingle = thisObj.makeObj($(this).find('pubDate').text(),
$(this).find('link').text(),
$(this).find('title').text(),
$(this).find('description').text(),
$(this).find('encoded').text(),
$(this).find('commentRss').text(),
$(this).find('comments').last().text());
thisObj.pubArray.push(pubSingle);
});
console.log(thisObj.pubArray); // OK
}
}, 'xml');
console.log(this.pubArray); // Empty
return (this.pubArray);
};
MyParser.prototype.makeObj = function (pubDate, pubLink, pubTitle, pubDesc, pubContent, pubComCount, pubComLink) {
"use strict";
var pubSingle = {};
pubSingle.pubDate = new Date(pubDate);
pubSingle.pubLink = pubLink;
pubSingle.pubTitle = pubTitle;
pubSingle.pubDesc = pubDesc;
pubSingle.pubContent = pubContent;
pubSingle.pubComCount = pubComCount;
pubSingle.pubComLink = pubComLink;
return (pubSingle);
};
}
this.init_ok = true;
}
If you look at the console.log(), you'll see that the line // OK is outputting my array correctly.
But later, when returning from $.get, my array is empty.
Does anybody have an idea why, and how to correct that please?
This is not a problem with variable-scope. The problem here is that you're working with asynchronous flow and you're not thinking correctly the flow.
Let me explain:
When you do your .get, you fire a parallel asynchronous process that will request information from the browser, but your main program's flow keeps going, so when you get to your "return" statement, your array has not been filled yet with the response from your get method.
You should use your array from inside the get callback and not outside of it, since you can't guarantee that the array will have the information you need.
Does it make any sense?
Let me know!
Further explanation
According to your comments, you're still doing something like this:
var results = MyParser(feed_url);
//code that uses results.pubArray
And you cannot do that. Even though you're setting your "pubArray" inside your .get callback, you're trying to use pubArray right after you called MyParser and that's before the .get callback is called.
What you have to do, is call your next step on your program's logic from within the .get callback... that's the only way you can be sure that the pubArray is filled with proper data.
I hope that makes it clearer.
This is because your line
console.log(this.pubArray); // Empty
is being called directly after you issue your Ajax request; it hasn't had time to fetch the data yet. The line
console.log(thisObj.pubArray); // OK
is being called inside the Ajax callback, by which time the data has been fetched.
Thank you all, and particulary #Deleteman .
Here is what I did:
$.get(this.feedUrl, 'xml').success(function () {
thisObj.handleAjax(arguments[0], arguments[1], arguments[2]);
$(document).trigger('MyParserDone');
}).error(function () {
$(document).trigger('MyParserFailed');
});
Then, when i enter "HandleAjax", i'm back in my object context, so "this" refers to my object and the right properties. The only "problem" is that I have to set a listener (MyParserDone) to make sure the parsing is finished.

Functional object basics. How to go beyond simple containers?

On the upside I'm kinda bright, on the downside I'm wracked with ADD. If I have a simple example, that fits with what I already understand, I get it. I hope someone here can help me get it.
I've got a page that, on an interval, polls a server, processes the data, stores it in an object, and displays it in a div. It is using global variables, and outputing to a div defined in my html. I have to get it into an object so I can create multiple instances, pointed at different servers, and managing their data seperately.
My code is basically structured like this...
HTML...
<div id="server_output" class="data_div"></div>
JavaScript...
// globals
var server_url = "http://some.net/address?client=Some+Client";
var data = new Object();
var since_record_id;
var interval_id;
// window onload
window.onload(){
getRecent();
interval_id = setInterval(function(){
pollForNew();
}, 300000);
}
function getRecent(){
var url = server_url + '&recent=20';
// do stuff that relies on globals
// and literal reference to "server_output" div.
}
function pollForNew(){
var url = server_url + '&since_record_id=' + since_record_id;
// again dealing with globals and "server_output".
}
How would I go about formatting that into an object with the globals defined as attributes, and member functions(?) Preferably one that builds its own output div on creation, and returns a reference to it. So I could do something like...
dataOne = new MyDataDiv('http://address/?client');
dataOne.style.left = "30px";
dataTwo = new MyDataDiv('http://different/?client');
dataTwo.style.left = "500px";
My code is actually much more convoluted than this, but I think if I could understand this, I could apply it to what I've already got. If there is anything I've asked for that just isn't possible please tell me. I intend to figure this out, and will. Just typing out the question has helped my ADD addled mind get a better handle on what I'm actually trying to do.
As always... Any help is help.
Thanks
Skip
UPDATE:
I've already got this...
$("body").prepend("<div>text</div>");
this.test = document.body.firstChild;
this.test.style.backgroundColor = "blue";
That's a div created in code, and a reference that can be returned. Stick it in a function, it works.
UPDATE AGAIN:
I've got draggable popups created and manipulated as objects with one prototype function. Here's the fiddle. That's my first fiddle! The popups are key to my project, and from what I've learned the data functionality will come easy.
This is pretty close:
// globals
var pairs = {
{ div : 'div1', url : 'http://some.net/address?client=Some+Client' } ,
{ div : 'div2', url : 'http://some.net/otheraddress?client=Some+Client' } ,
};
var since_record_id; //?? not sure what this is
var intervals = [];
// window onload
window.onload(){ // I don't think this is gonna work
for(var i; i<pairs.length; i++) {
getRecent(pairs[i]);
intervals.push(setInterval(function(){
pollForNew(map[i]);
}, 300000));
}
}
function getRecent(map){
var url = map.url + '&recent=20';
// do stuff here to retrieve the resource
var content = loadResoucrce(url); // must define this
var elt = document.getElementById(map.div);
elt.innerHTML = content;
}
function pollForNew(map){
var url = map.url + '&since_record_id=' + since_record_id;
var content = loadResoucrce(url); // returns an html fragment
var elt = document.getElementById(map.div);
elt.innerHTML = content;
}
and the html obviously needs two divs:
<div id='div1' class='data_div'></div>
<div id='div2' class='data_div'></div>
Your 'window.onload` - I don't think that's gonna work, but maybe you have it set up correctly and didn't want to bother putting in all the code.
About my suggested code - it defines an array in the global scope, an array of objects. Each object is a map, a dictionary if you like. These are the params for each div. It supplies the div id, and the url stub. If you have other params that vary according to div, put them in the map.
Then, call getRecent() once for each map object. Inside the function you can unwrap the map object and get at its parameters.
You also want to set up that interval within the loop, using the same parameterization. I myself would prefer to use setTimeout(), but that's just me.
You need to supply the loadResource() function that accepts a URL (string) and returns the HTML available at that URL.
This solves the problem of modularity, but it is not "an object" or class-based approach to the problem. I'm not sure why you'd want one with such a simple task. Here's a crack an an object that does what you want:
(function() {
var getRecent = function(url, div){
url = url + '&recent=20';
// do stuff here to retrieve the resource
var content = loadResoucrce(url); // must define this
var elt = document.getElementById(div);
elt.innerHTML = content;
}
var pollForNew = function(url, div){
url = url + '&since_record_id=' + since_record_id;
var content = loadResoucrce(url); // returns an html fragment
var elt = document.getElementById(div);
elt.innerHTML = content;
}
UpdatingDataDiv = function(map) {
if (! (this instanceof arguments.callee) ) {
var error = new Error("you must use new to instantiate this class");
error.source = "UpdatingDataDiv";
throw error;
}
this.url = map.url;
this.div = map.div;
this.interval = map.interval || 30000; // default 30s
var self = this;
getRecent(this.url, this.div);
this.intervalId = setInterval(function(){
pollForNew(self.url, self.div);
}, this.interval);
};
UpdatingDataDiv.prototype.cancel = function() {
if (this.intervalId) {
clearInterval(this.intervalId);
this.intervalId = null;
}
}
})();
var d1= new UpdatingDataDiv('div1','http://some.net/address?client=Some+Client');
var d2= new UpdatingDataDiv('div2','http://some.net/otheraddress?client=Some+Client');
...
d1.cancel();
But there's not a lot you can do with d1 and d2. You can invoke cancel() to stop the updating. I guess you could add more functions to extend its capability.
OK, figured out what I needed. It's pretty straight forward.
First off disregard window.onload, the object is defined as a function and when you instantiate a new object it runs the function. Do your setup in the function.
Second, for global variables that you wish to make local to your object, simply define them as this.variable_name; within the object. Those variables are visible throughout the object, and its member functions.
Third, define your member functions as object.prototype.function = function(){};
Fourth, for my case, the object function should return this; This allows regular program flow to examine the variables of the object using dot notation.
This is the answer I was looking for. It takes my non-functional example code, and repackages it as an object...
function ServerObject(url){
// global to the object
this.server_url = url;
this.data = new Object();
this.since_record_id;
this.interval_id;
// do the onload functions
this.getRecent();
this.interval_id = setInterval(function(){
this.pollForNew();
}, 300000);
// do other stuff to setup the object
return this;
}
// define the getRecent function
ServerObject.prototype.getRecent = function(){
// do getRecent(); stuff
// reference object variables as this.variable;
}
// same for pollForNew();
ServerObject.prototype.pollForNew = function(){
// do pollForNew(); stuff here.
// reference object variables as this.variable;
}
Then in your program flow you do something like...
var server = new ServerObject("http://some.net/address");
server.variable = newValue; // access object variables
I mentioned the ADD in the first post. I'm smart enough to know how complex objects can be, and when I look for examples and explanations they expose certain layers of those complexities that cause my mind to just swim. It is difficult to drill down to the simple rules that get you started on the ground floor. What's the scope of 'this'? Sure I'll figure that out someday, but the simple truth is, you gotta reference 'this'.
Thanks
I wish I had more to offer.
Skip

JQuery - accessing a VAR in a function which I will need in another function?

Ok so in my html/js i have a form that updates based on the users previous selection. On the last stage i have a select menu where the user will choose their city. I have stored the value of the selected item in my Options list with the id #myCity to the following.
('#myCity').change(function(){
var CityValue = $("#myCity").val();
});
Once that value is set, my form then displays the submit button
<input type="submit" id="go" value="Submit" onclick="getweather()" />
This is where i start to have a bit of bother. In my getweather() function i want to be able to take the var CityValue from above and append it to another var so i can load a specific page.
function getweather(){
var CityValue;
var to_load = 'getweather.php?p='+ CityValue +'.html';
$('#weather').empty().append(to_load);
}
but in my testing i do not think that my getweather() function is able to read my desired var. Can anyone suggest a solution?
Well, the first function you specified (the event handler for onchange) doesn't do anything right now. You can just remove it and edit the second function like this:
function getweather(){
var CityValue = $("#myCity").val();
var to_load = 'getweather.php?p='+ CityValue +'.html';
$('#weather').empty().append(to_load);
}
You declared the CityValue only in the function scope that you cannot access from outside. Either declare your variable globally:
var CityValue;
$('#myCity').change(function(){
CityValue = $("#myCity").val();
});
function getweather() {
var to_load = 'getweather.php?p='+ encodeURIComponent(CityValue) +'.html';
$('#weather').empty().append(to_load);
}
Or just call $("#myCity").val() in your getweather function:
function getweather() {
var to_load = 'getweather.php?p='+ encodeURIComponent($("#myCity").val()) +'.html';
$('#weather').empty().append(to_load);
}
Well, the first function you specified (the event handler for onchange) doesn't do anything right now. You can just remove it and edit the second function like this:
You can then add this function call to the change event.
function getweather(){
var CityValue = $("#myCity").val();
var to_load = 'getweather.php?p='+ CityValue +'.html';
$('#weather').empty().append(to_load);
}
$('#myCity').change(getweather);
The more elegant answer to the question is in using jQuery data API. This allows you to store arbitrary data within an object rather than declaring variables, keeping everything in a nice OOP manner. So, to do what you want would mean storing the value like so:
$('#myCity').change(function(){
$("#myCity").data("CityValue", $("#myCity").val());
});
This way you would be able to retrieve it like so:
function getweather(){
var to_load = 'getweather.php?p='+ $("#myCity").data("CityValue") +'.html';
$('#weather').empty().append(to_load);
}

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