I have the javascript code for a link click:
document.getElementById('giddy').onclick = function {
alert(this.href);
};
and I want to separate the function part of it...I have
document.getElementById('giddy').onclick = poro(this);
function poro(yyyy) {
alert(yyyy.href);
};
But it is not working (says undefined in the alert)...what am I doing wrong?
You don't need to pass this as a parameter. this will be the context for the function when it is called. You should just have:
document.getElementById('giddy').onclick = poro;
function poro() {
alert(this.href);
};
Get rid of (this) and use this in the function instead of yyyy.
document.getElementById('giddy').onclick = poro;
function poro() {
alert(this.href);
};
You're immediately calling the poro function.
Essentially, you're telling Javascript that the element's onclick value will equal the result of calling the poro(this [window] ) function.
To get around this, you can wrap the poro(this) function inside an empty function, like so:
document.getElementById('giddy').onclick = function(){poro(this)} function poro(yyyy) { alert(yyyy.href); };
You may also want to consider using an eventListener, as it allows room for expansion.
Almost there! You should do:
document.getElementById('giddy').onclick = function(){ poro(this); }
function poro(yyyy) {
alert(yyyy.href);
};
Note poro(this); wrapped in an anonymous function.
I'd recommend using addEventListener instead of the onclick method.
Try this:
var giddy = document.getElementById('giddy');
giddy.addEventListener('click', function(e) { poro(this); }, false);
function poro(yyyy) {
alert(yyyy.href);
}
since you are using jquery use :
$('#giddy').click(function(){ poro($(this));});
or you can use the bind() function
$("#giddy").bind("click", $(this), poro);
Related
$('#homeNavBar').on('click', onSiteLoad());
function onSiteLoad() {
$('#dataHolder').html('');
userLoginMenu.html('');
var h1 = $('<h1>').text('Welcome');
var span = $('<span>').text('Welcome to our book library');
dataHolder.append(h1).append(span);
}
I want to call the function onSiteLoad() directly inside change function.
The only way it lets me do it is like this:
$('#homeNavBar').on('click', function () {
$('#dataHolder').html('');
userLoginMenu.html('');
var h1 = $('<h1>').text('Welcome');
var span = $('<span>').text('Welcome to our book library');
dataHolder.append(h1).append(span);
});
You need to pass the function reference, as of now you are invoking the function as passing its return value an event handler
$('#homeNavBar').on('click', onSiteLoad);
//^^^^ Parenthesis removed
You can call the external function inside your onClick also.
$('#homeNavBar').on('click', function () {
onSiteLoad();
});
Here's the code:
window.onload = function() {
oldonload && oldonload();
function test() {
alert("meh");
}
$('input[type=file]').change(test());
}
The code is fairly straight forward, test() is called only when input[type=file] is changed. However test() is being called whenever my page is loaded.
What is going on here? How would I execute the function only when user interacts with the input element?
You are calling the method on this line:
$('input[type=file]').change(test());
Change it to:
$('input[type=file]').change(test);
If you want to pass a parameter to test:
var myVar = 5;
$('input[type=file]').change(function () {
test(myVar);
});
Just change the file change event like this :
$('input[type=file]').change(function() { test() });
You're executing the function immedietaly instead of assigning a handler. You should instead do:
$('input[type=file]').change(test);
change takes function as argument, so you just need to provide function name to be called.
$('input[type=file]').change(test);
I would like to pass a function with parameters to another function and have it run on an event, like this:
var main_object = function () {
this.main_function = function (function) {
document.addEventListener('click',function);
}
this.passed_function = function (variable) {
alert(variable);
}
}
var main_object = new main_object();
main_object.main_function(main_object.passed_function(3));
In modern JavaScript engines, you can bind the function:
mainObject.main_function(main_object.passed_function.bind(main_object, 3));
The first argument to bind will be this when the function executes and any remaining arguments to bind will be leading arguments in the call to the function.
If I understand you right,
main_object.main_function(function() { main_object.passed_function(3) });
For what you're talking about, you could just use bind. In your case, you would do:
main_object.main_function(main_object.passed_function.bind( main_object, 3 ));
function mainfunc(func) {
alert(func);
}
function callBackFn(a) {
alert(a);
}
mainfunc("arg1", callBackFn("javaScritFnParameter")); //call this in load
For sure it works no need to worry... but callbackFn will execute first and next only "arg1" will execute.
I have a function that listens for a click on the screen and fires a callback. It is part of a Helper object (which is why is preceded by the term Helper in my sample code. That is irrelevant however.
var Helper = {
bodyClickListener: function(fn) {
var window = document.getElementsByTagName('body')[0];
window.click();
CORE.dom.on(window, 'click', function(event) {
CORE.dom.off(window, 'click');
fn(event);
});
}
}
I need to be able to pass a function into this function with a parameter that has been previously set.
function someFunction() {
var popup = document.getElementById('tagResultsPopup');
Helper.bodyClickListener(function(popup) {
return function(event) {
event.stopPropagation();
removePopup(popup);
};
}(document.getElementById('tagResultsPopup')));
function removePopup(element) {
if(element) {
element.parentNode.removeChild(element);
}
};
}
The code above works, but you'll notice that I have to set the popup variable inside of the callback function. It has already been set above. How do I pass a reference to the earlier variable into the callback function.
If I understand your question correctly, you don't need to do much. You can just use the popup variable defined outside.
var popup = document.getElementById('tagResultsPopup');
Helper.bodyClickListener(function(event) {
event.stopPropagation();
//Don't set it
//var popup = document.getElementById('tagResultsPopup');
removePopup(popup);//popup will refer to the correct variable
});
The function that you are passing to bodyClickListener is a closure. You can simply reference 'popup' inside that function without any problem. You don't have to create a new variable.
The answer was to use closure in this way:
Helper.bodyClickListener(function(popup) {
return function(event) {
event.stopPropagation();
removePopup(popup);
};
}(document.getElementById('tagResultsPopup')));
That way the callback function has access to the variable I pass into the parameter function. So here, the return is actually the function I am passing as the callback.
Is this how you define a function in jQuery?
$(document).ready( function () {
var MyBlah = function($blah) { alert($blah); };
});
Now to call the function I do:
MyBlah('hello');
First of all, your code works and that's a valid way of creating a function in JavaScript (jQuery aside), but because you are declaring a function inside another function (an anonymous one in this case) "MyBlah" will not be accessible from the global scope.
Here's an example:
$(document).ready( function () {
var MyBlah = function($blah) { alert($blah); };
MyBlah("Hello this works") // Inside the anonymous function we are cool.
});
MyBlah("Oops") //This throws a JavaScript error (MyBlah is not a function)
This is (sometimes) a desirable behavior since we do not pollute the global namespace, so if your function does not need to be called from other part of your code, this is the way to go.
Declaring it outside the anonymous function places it in the global namespace, and it's accessible from everywhere.
Lastly, the $ at the beginning of the variable name is not needed, and sometimes used as a jQuery convention when the variable is an instance of the jQuery object itself (not necessarily in this case).
Maybe what you need is creating a jQuery plugin, this is very very easy and useful as well since it will allow you to do something like this:
$('div#message').myBlah("hello")
See also: http://www.re-cycledair.com/creating-jquery-plugins
No, you can just write the function as:
$(document).ready(function() {
MyBlah("hello");
});
function MyBlah(blah) {
alert(blah);
}
This calls the function MyBlah on content ready.
No.
You define the functions exactly the same way you would in regular javascript.
//document ready
$(function(){
myBlah();
})
var myBlah = function(blah){
alert(blah);
}
Also: There is no need for the $
You can extend jQuery prototype and use your function as a jQuery method.
(function($)
{
$.fn.MyBlah = function(blah)
{
$(this).addClass(blah);
console.log('blah class added');
};
})(jQuery);
jQuery(document).ready(function($)
{
$('#blahElementId').MyBlah('newClass');
});
More info on extending jQuery prototype here: http://api.jquery.com/jquery.fn.extend/
jQuery.fn.extend({
zigzag: function () {
var text = $(this).text();
var zigzagText = '';
var toggle = true; //lower/uppper toggle
$.each(text, function(i, nome) {
zigzagText += (toggle) ? nome.toUpperCase() : nome.toLowerCase();
toggle = (toggle) ? false : true;
});
return zigzagText;
}
});
The following example show you how to define a function in jQuery. You will see a button “Click here”, when you click on it, we call our function “myFunction()”.
$(document).ready(function(){
$.myFunction = function(){
alert('You have successfully defined the function!');
}
$(".btn").click(function(){
$.myFunction();
});
});
You can see an example here: How to define a function in jQuery?
That is how you define an anonymous function that gets called when the document is ready.