JQuery :: Use Of This Keyword With And Without String
Aug 29, 2011
I was reading thegetting started with jquery. And got confused with use of this in these 2 code segments.
$(document).ready(function() {
$("#orderedlist").find("li").each(function(i) {
$(this).append( " BAM! " + i );
});
});
$(document).ready(function() {
// use this to reset several forms at once
$("#reset").click(function() {
$("form").each(function() {
this.reset();
});
});
When do we need $(this) and this? And what is the difference between them?
I've just started learning jquery and have been trying to use this code which I found on this forum.I want to detect some text (addClients) in the url and add an css id to a list item with the class m1 (li class="m1") - so I get (li class="m1" id="expanded"):
This is what I have so far (which is not working)$(function() { $(document).ready(function() { var url = location.pathname;
My plan is to create a JavaScript class, with some functions and variables, and one of the functions is called when a user clicks on a certain element. However, I need to find out the ID of the element that was clicked (in the example, that of the <p>) for further processing. It looks basically like the following:
[Code]...
The result was very crazy, because console.log(this) gave me the node as result, and console.log($(this)) did the same only as jQuery node, but trying to find out the attribute via jQuery gave undefined as result. I haven't checked if this.id would work (should probably), but I'd prefer to keep the whole script in jQuery, if possible. I suspect it may be an overusage of the 'this' keyword, but if so, what's the proper way to do it?
I am modifying the suckerfish dropdown code to use settimeout to have a slight pause before the menus disappear to make it more user friendly. I have hit a snag with the following statement:
out of the settimeout function, it works. (w/o the pause, obviously). With the settimeout function, I get "this.getElementByTagName is not a function" error.
I have tried putting this.getElementsByTagName("UL")[0] is a variable and then using that in the settimeout function, but then each li will only open the very last menu in the list. (ie all the menu items open the last sub menu) Code:
I've been searching google endlessly and I've come to the conclusion I'm not using the proper search keywords. I'm trying to create something similar to the banner/button combo you can find here:[URL]..
I assume these type of slide show buttons combos use java script and possibly php. If anyone knows the proper name for this type of slide show or can point me to some scripting
Would like to check if there is anyway where i can use javascript to grab the keyword of .doc and .pdf file.
because when i right-click on the files, and click on properties. there will be a tab at the top (Summary for .doc and PDF for .pdf), and upon clickin there will the description, author and keywords. so im just wondering if there is any way to grab the value?
I could just give each image an ID and not use the 'this' keyword, but I haven't used it much so I'm curious about it. It's sending the image element to the function, so why can't I modify the src attribute with that information?
I'm creating a list with buttons that show and hide some of the list elements to create the effect of scrolling. I've built an scrollList object so I can apply this to any list. When you create the object and pass it the id of the <ul> and how many items of the list you want to be displayed. It will add the scroll down and scroll up links and add an Event.observe to them (I'm using the Prototype library).
This code creates the object
var main_news_articles; main_news_articles = new scrollList('main_news_articles', 5); main_news_articles.init();
The problem I am having is with the callback functions of the onclick event of the links (scrollUp and scrollDown). The this keyword within these functions is refering to the link and not the object.
To try and solve this I've made the title attribute of the link the same as the variable name of the scrollList object. I can reference the scrollList object like so Code:
I am looking to insert a keyword in to a javascript alert box when someone visits my website, so say they came from codingforums, it would say "Welcome, CodingForums.com Visitor". My keyword will be passed from the ad platform I am working with and shows up correctly in the tracking, so I'd imagine it's just a case of having the snippet of code for it to show in the alert, correct? If there is no keyword, I would just like it to say "Welcome Visitor" or something.
I want to use the new keyword to instantiate an object. The catch is I want to pass in variable length arguments. Given: function Foo () { this.args = Array.prototype.join.call (arguments); }var args = ["arg0", "arg1", "arg2"];
The following don't work (though I understand why): new Foo.apply (null, args); new (Foo.apply (null, args)); (new Foo).apply (null, args); How to do what I want without modifying Foo's source code?
// simplified to remove all the try/catches & stuff function newXHR() { request = new XMLHttpRequest(); XMLHttpRequest.prototype.requested = null; return request; }
then later:
function doRequest(url, callback) { var req = newXHR(); req.requested = url;
// et cetera.... }
This works fine in Firefox, however the line 'req.requested = url' causes an error in IE7, (I haven't tested IE6 yet). The error is 'Object doesn't support this property or method'
So, this leads me to believe that either a) XMLHttpRequest.requested is not writable, or, b) XMLHttpRequest.requested was never created in the first place. I think it's the first option because I'm not getting an error in the newXHR() function.
I've been searching for some documentation on this but I can't seem to find anywhere if properties created with the prototype keyword are writeable in IE. Does anyone know what the problem is?
So I know all about the caviats of the 'this' keyword when calling object functions from event listeners:
Code: var foo = {bar: true, zoo: function() { return this.bar; }}; foo.zoo(); > true a = foo.zoo; a(); >
And I know that I can get around this by using an anonymous function so that 'this' is preserved in it's original context:
[Code]...
But then someone pointed out this article on memory leaks when using anonymous functions to call object methods because the anonymous function gets access to ALL variables in the enclosing environment and my not be properly disposed of by the garbage collector [URL] So that lead me to think about using a "3rd-person" approach to referencing object properties from within object methods.
How can I grab the keyword phrase that someone used to enter the website and then pass that through a form? I would need to know for search engines and Google AdWords as well. Does anyone know how to do this?
is it possible to combine the the following functions with each other in an array for example and if so, would someone be kind enough to show me how. the reasons are 1. to see if it is at all possible and 2. to learn so that I can combine further possibilities in the future. the first script compares user keywords from search mashines and the second replaces certain strings/paterns with others.
I am confused about what the return keyword is actually returning when returning an object, a primitive, or a function. My confusion is compounded by the fact that I'm not sure if a function is an object or not. According to the book JavaScript Programmer Reference it is: "All functions in JavaScript are first class objects , meaning they can be passed around like any other object reference. In fact, regardless of how they are created, functions are instances of a global object named (aptly) Function."
However, someone else states that a function is not an object. An object is a set of primitives and references. A function is executable code. Functions become objects through the use of the new operator. Yet, in the book I mentioned, it says you don't need the new keyword to execute the function as an object, as it already inherits from the object Function when the function keyword is used:
function functionName([argname1 [, ...[, argnameN]]]) { statements; }
So there's one source of contradiction. Now the bigger issue is what is going on when the return keyword is used. Notice the Validation() function returns an object as its last expression. This technique is common, where you return an object which contains functions in form of object notation. I believe this is done so that we create a closure so that when the intepreter exits the Validation() method, since we created a closure by returning an object, which contains the inner functions addRule and getRule, the local variables of Validation() are not destroyed, given that we can reference them through the two inner functions that make use of the local variables of the outer function. So when we use the return keyword on an object literal, and then exit the function, when we call one of the inner functions as we do later:
First of all excuse me if I posted this thread in the wrong forum, I really have no clue where to put this but I've had some minor experience with js so I hope it can be solved this way. I check websites and/or keywords in googles Keyword Tool External as a free service for some of my clients. The thing is that more and more clients like this service and it's becoming very time-consuming for me to do this for all of them.
Is there a way to let my clients fill in the keywords or url they like researched in a form on my website, then let those words be researched and return a specified number of results in a pdf or something? My biggest concern is the captcha code. If I can't find a way to partially or fully automate this process, I'll be forced to either charge for or completely give up this service.
I need a simple, quick and efficient way to logically branch if I find a string is contained in another string in jquery Most other languages this can be resolved in one or two lines and it would be readable.
I have a simple example below showing how when I pass in the value of the value attribute of option node, and then use if operator to check whether parameter is a string or not, even though it's a string, it converts it to false boolean and triggers the else statement rather than calling a function.callback should be a string so why is it saying otherwise?
