I'm trying to add a pause between clicks when clicking on buttons in a page.
It's giving me "Uncaught TypeError: Cannot read property 'click' of undefined"
var inputs = document.getElementsByClassName('xxxxxx');
for(var i=0;i<inputs.length;i++) {
setTimeout(function() {
inputs[i].click();
}, (1000 * i))
}
Not sure how else to approach it. If I remove the timeout, the clicks work properly.
This is a problem called "closing over the loop variable". What's happening is that when your timeout actually fires, i is equal to inputs.length, which is beyond the end of the set of inputs.
Simplest solution: use Array#forEach so that you have a separate closure containing each input itself and a separate, non-fluctuating copy of i, instead of an i variable that keeps changing:
var inputs = document.getElementsByClassName('xxxxxx');
Array.prototype.slice.call(inputs).forEach(function (input, i) {
setTimeout(function () {
input.click();
}, 1000 * i);
});
Try testing for the input if null :
if (inputs[i] != null) {
inputs[i].click();}
and try starting the timer on document complete.
Related
This is originally from (Pause execution in while loop locks browser (updated with fiddles))
I have been at this all day and I can't figure out how to keep javascript from advancing to the next line and in essence executing all lines at once. I have tried every combination of delay / setTimeout I can think of to no avail.
I just want the elements in the array to flash once then pause, then do it again for another element in the array till all elements have been removed and the array is empty.
But because javascript is executing all lines at once I end up with the appearance of all elements flashing at the same time.
Here is the fiddle:
http://jsfiddle.net/ramjet/xgz52/7/
and the relevant code:
FlashElement: function () {
while (elementArray.length) {
alert('a ' + elementArray.length);
var $el = elementArray.eq(Math.floor(Math.random() * elementArray.length));
PageLoadAnimation.FlashBlast($el);
alert('delay complete');
elementArray = elementArray.not($el);
alert('array popped');
alert('z ' + elementArray.length);
}
},
ANSWER FOR THIS SITUATION. Hopefully it will help others.
As Zach Saucier points out the loop was really my problem...but not the only problem. I was the other problem(s).
Me first.
Fool that I am I was really causing my own complications with two things I was doing wrong.
First using jsfiddle my javascript would error due to syntax or some such thing but fiddle doesn't tell you that (to my knowledge) so my fiddle wouldn't run but I took it in pride as MY CODE IS FINE stupid javascript isn't working.
Second I was passing my function to setTimeout incorrectly. I was adding the function parens () and that is not correct either which would bring me back to issue one above.
WRONG: intervalTimer = setInterval(MyFunction(), 1500);
RIGHT: intervalTimer = setInterval(MyFunction, 1500);
As for the code. As Zach pointed out and I read here (http://javascript.info/tutorial/settimeout-setinterval) while he was responding setting a timeout in a loop is bad. The loop will iterate rapidly and with the timeout one of the steps in the loop we get into a circular firing squad.
Here is my implementation:
I created a couple variables but didn't want them polluting the global scope so I created them within the custom domain. One to hold the array of elements the other the handle to the setInterval object.
var PageLoadAnimation =
{
elementArray: null,
intervalTimer: null,
....
}
In my onReady function (the one the page calls to kick things off) I set my domain array variable and set the interval saving the handle for use later. Note that the interval timer is how long I want between images flashes.
onReady: function ()
{
elementArray = $('#PartialsContainer').children();
//black everything out just to be sure
PageLoadAnimation.BlackOutElements();
//flash & show
intervalTimer = setInterval(PageLoadAnimation.FlashElement, 1500);
},
Now instead of looping through the array I am executing a function at certain intervals and just tracking how many elements are left in the array to be flashed. Once there are zero elements in the array I kill the interval execution.
FlashElement: function ()
{
if(elementArray.length > 0) //check how many elements left to be flashed
{
var $el = PageLoadAnimation.GrabElement(); //get random element
PageLoadAnimation.FlashBlast($el); //flash it
PageLoadAnimation.RemoveElement($el); //remove that element
}
else
{
//done clear timer
clearInterval(intervalTimer);
intervalTimer = null;
}
},
So the whole thing is:
var PageLoadAnimation =
{
elementArray: null,
intervalTimer: null,
onReady: function () {
elementArray = $('#PartialsContainer').children();
//black everything out just to be sure
PageLoadAnimation.BlackOutElements();
//flash & show
intervalTimer = setInterval(PageLoadAnimation.FlashElement, 1500);
//NOT this PageLoadAnimation.FlashElement()
},
BlackOutElements: function () {
$('#PartialsContainer').children().hide();
},
FlashElement: function ()
{
if(elementArray.length > 0)
{
var $el = PageLoadAnimation.GrabElement();
PageLoadAnimation.FlashBlast($el);
PageLoadAnimation.RemoveElement($el);
}
else
{
//done clear timer
clearInterval(intervalTimer);
intervalTimer = null;
}
},
GrabElement: function()
{
return elementArray.eq(Math.floor(Math.random() * elementArray.length));
},
RemoveElement: function($el)
{ elementArray = elementArray.not($el); },
FlashBlast: function ($el) {
//flash background
$el.fadeIn(100, function () { $el.fadeOut(100) });
}
}
Hope that help others understand the way to go about pausing execution in javascript.
The reason why you were having trouble is because setTimeout function is non-blocking and will return immediately. Therefore the loop will iterate very quickly, initiating each of the timeouts within milliseconds of each other instead of including the previous one's delay
As a result, you need to create a custom function that will wait on the setInterval to finish before running again
FlashElement: function () { // Call it where you had the function originally
myLoop();
},
...
function myLoop() {
setTimeout(function () { // call a setTimeout when the loop is called
var $el = elementArray.eq(Math.floor(Math.random() * elementArray.length));
PageLoadAnimation.FlashBlast($el);
elementArray = elementArray.not($el);
if (0 < elementArray.length) { // if the counter < length, call the loop function
myLoop();
}
}, 1000)
}
Feel free to change the delay to whatever value you wish (3000ms to let each fade finish before the last at the moment). If you want to start the fade in of the next before the previous ends and keep them in their original positions you would have to animate the opacity using .css instead of using fadeIn and fadeOut
My answer is based on this answer from another SO question
I have the following code
startProgressTimer: function () {
var me = this,
updateProgressBars = function (eventItems) {
alert("updateProgressBars: looping");
alert("me.eventProgressTimerId:" + me.eventProgressTimerId);
var i = 0;
if (eventItems.length === 0) {
alert("internal Stop Begin")
clearInterval(me.eventProgressTimerId);
alert("internal Stop End")
eventItems = [];
}
for (i = 0; i < eventItems.length; i++) {
if (eventItems[i]._eventId) {
eventItems[i].updateProgressBar();
}
}
};
alert("Start Progress Timer");
this.eventProgressTimerId = setInterval(function () {
updateProgressBars([]);
}, 10000);
}
When the function is called I would expect it to run and bottom out only it keeps on looping.
screen output
ALERT:updateProgressBars: looping
ALERT:me.eventProgressTimerId:10
ALERT:internal Stop Begin
ALERT:internal Stop End
ALERT:updateProgressBars: looping
ALERT:me.eventProgressTimerId:10
ALERT:internal Stop Begin
ALERT:internal Stop End
Any ideas
I suspect the problem might be that the code you don't show calls the startProgressTimer() method more than once for the same instance of whatever object it belongs to, and then within the method you store the interval id in an instance property this.eventProgressTimerId - so multiple calls overwrite the property and you'd only be able to cancel the last one.
If that's the case, a simple fix is to declare your eventProgressTimerId as a local variable within startProgressTimer().
I have a search box that hides all lines in a list that don't contain the entered text.
This worked great until the list became 10,000 lines long. One keystroke is fine but if the user types a several letter word, the function is iterated for each keypress.
What I want to do is to abandon any previous execution of the function if a new key is pressed.
The function is very simple, as follows:
$("#search").keyup(function(e) {
goSearch();
});
function goSearch()
{
var searchString = $("#search").val().toLowerCase();
$(".lplist").each(function(index, element) {
var row = "#row-" + element.id.substr(5);
if ($(element).text().toLowerCase().indexOf(searchString,0) != -1)
$(row).show();
else
$(row).hide();
});
}
Thanks
You can't directly. Javascript is not multi-threaded so your function will run and block any key-presses until it is done.
The way this is made tolerable from a user-experience point of view is to not trigger a function immediately on a key event, but to wait a short period of time and then fire the event.
While the user is typing, the timeout function will continually be set and reset and so the gosearch function won't be called, and so the user won't have their typing interrupted.
When the user pauses typing, the timeout will countdown to zero and call the search function, which will run and block typing until it completes. But that's okay (so long as it completes within a second or so) as the user is probably not currently trying to type.
You can also do what you actually asked by breaking up your gosearch function into chunks, where each call to the function: * Reads a counter of the number of lines processed so far, and then processes another 500 lines and increments the counter. * Calls another gosearch using setTimeout with a value of zero for the time. This yields events to other 'threads', and allows for fast changing of search terms.
var goSearchTimeout = null;
var linesSearched = 0;
function keySearch(e){
if(goSearchTimeout != null){
clearTimeout(goSearchTimeout);
linesSearched = 0;
}
goSearchTimeout = setTimeout(goSearch, 500);
}
$("#search").keyup(keySearch);
function highLight(index, element) {
if(index >= linesSearched){
var row = "#row-" + element.id.substr(5);
if ($(element).text().toLowerCase().indexOf(searchString,0) != -1){
$(row).show();
else{
$(row).hide();
}
if(index > linesSearched + 500){
linesSearched = index;
goSearchTimeout = setTimeout(goSearch);
return;
}
}
function goSearch(){
goSearchTimeout = null;
var searchString = $("#search").val().toLowerCase();
$(".lplist").each(highLight);
}
If you're going to use timeout callbacks like this, I'd strongly recommend wrapping your code up into jQuery widgets, so that you can use variables on the object to store the variables goSearchTimeout etc rather than having them float around as global variables.
Introduce a counter var keypressCount that is being increased by your keypress event handler. at the start of goSearch() write its value into a buffer. Then at each run of your $(".lplist").each() you ask if the current keypressCount is the same as the buffered one; if not, you return. I would suggest you use a for() though since it is easier to break; than $.each().
Update:
You will have to make sure that there is time for new keypress events to be fired/received, so wrap the anonymous function of your $.each() inside a timeout.
Reference: http://www.garrickcheung.com/javascript/what-i-learned-about-multi-threading-in-javascript/
You can use a global variable to save search string and stop execution when search string changes.
IMPORTANT: You must set a timeout in each iteration so that function execution is paused and global variables are updated, as JavaScript is single-threaded.
Your code would look like this:
var searchString;
$("#search").keyup(function(e) {
// Update search string
searchString = $("#search").val().toLowerCase();
// Get items to be searched
var items = $(".lplist");
// Start searching!
goSearch(items, searchString, 0);
});
function goSearch(items, filter, iterator)
{
// Exit if search changed
if (searchString != filter) {
return;
}
// Exit if there are no items left
if (iterator >= items.length) {
return;
}
// Main logic goes here
var element = items[iterator];
var row = "#row-" + element.id.substr(5);
if ($(element).text().toLowerCase().indexOf(filter, 0) != -1)
$(row).show();
else
$(row).hide();
// Schedule next iteration in 5 ms (tune time for better performance)
setTimeout(function() {
goSearch(items, filter, iterator + 1);
}, 5);
}
Im trying to assign an onKeyUp event to all inputs within a form, using closures. the array fields contains all the names of the fields that require the event assigned to them. The array ajaxFields contains the names of the fields (from the array fields) that requires ajax validation.
function createEvents(fields,ajaxFields) {
for(var x=0;x<fields.length;x++) {
$('input[name='+fields[x]+']').keyup(function(field) {
//assign an onKeyUp event
return function() {
//some code using variable 'field' and array 'ajaxFields'
}(fields[x]));
}
}
I would like the onKeyUp function to be executed a second after the user has finished typing in that field, insted of every time the key is up (onKeyUp). this would save up a lot of processing space, not to mention the ajax calls. So far im using this:
clearTimeout(timer);
timer = setTimeout('validate()' ,1000);
You might have noticed that the function validate() doesn't exist, and thats because I dont know how to wrap the closures inside a named function, and im not even sure if I should...
So how do I do that?
EDIT: here is a current fiddle
You can (and should) pass functions to setTimeout instead of strings.
clearTimeout(timer);
timer = setTimeout(function(){
// your code here
}, 1000);
So, in your keyup, try something like this:
$('input[name='+fields[x]+']').keyup(function(field) {
//assign an onKeyUp event
return function() {
var that = this,
$this = $(this);
clearTimeout($this.data('timeout'));
$this.data('timeout', setTimeout(function(){
//some code using variable 'field' and array 'ajaxFields'
// "this" will not be your element in here, make sure to use "that" (or "$this")
}, 1000));
};
}(fields[x]));
I save the timeout in $this.data, so that each element can have its own timeout, instead of using a global variable.
Updated Demo: http://jsfiddle.net/Z43Bq/3/
This is what your code should look like:
var timer;
$(document).ready(function() {
var fields = $('.field');
var ajaxFields = $('.ajax-field');
createEvents(fields, ajaxFields);
});
function createEvents(fields,ajaxFields) {
// Use jQuery's "foreach" method
$(fields).each(function(inx, field) {
// Bind the listener here
$(field).keyup(function(ev) {
// Clear timeout if necessary
if (timer != null) clearTimeout(timer);
// Set the timeout
timer = setTimeout(function() {
// Your code should here
console.log('Fields: ', fields, '\nAjax Fields: ', ajaxFields, '\nTHE field: ', field);
}, 1000);
});
});
}
Also checkout the fiddle for the working code: http://jsfiddle.net/BLyhE/
//I have the following function:
function handle_message(msg)
{
//do work
console.log('some work: '+msg.val);
//call next message
msg.next();
}
//And array of message objects:
var msgs = [ {val : 'first msg'}, { val : 'second msg'}, { val : 'third msg'}];
//I link messages by setting next parameter in a way that it calls handle_message for the next msg in the list. Last one displays alert message.
msgs[2].next = function() {alert('done!')};
msgs[1].next = function() {handle_message(msgs[2]);};
msgs[0].next = function() {handle_message(msgs[1]);};
//Start the message handle "chain". It works!
handle_message(msgs[0]);
//======== Now I do exactly the same thing but I link messages using the for loop:
for (var i=msgs.length-1; i>=0; i--)
{
if (i==msgs.length-1)
{
msgs[i].next = function() {alert('done!');};
}
else
{
msgs[i].next = function() {handle_message(msgs[i+1]);};
}
}
//Start the message handling chain. It fails! It goes into infinite recursion (second message calls itself)
handle_message(msgs[0]);
Can sombody explain why it happens? Or maybe an alternative to this pattern? My case is this: I receive an array with messages and I have to handle them in order, one ofter another SYNCHRONOUSLY. The problem is some of the messages require firing a series of animations (jqwuery animate() which is async) and the following messages cannot be handled until the last animation is finished. Since there is no sleep() in javascript I was trying to use such pattern where the message calls the next one after it is finished (in case of animations I simply pass the 'next' function pointer to animate's "complete" callback). Anyway, I wanted to build this 'chain' dynamically but discovered this strange (?) behaviour.
You need a closure to make it work:
function handle_message( msg ) {
console.log( 'some work: ' + msg.val );
msg.next();
}
var msgs = [{val :'first msg'},{val:'second msg'},{val:'third msg'}];
for ( var i = msgs.length - 1; i >= 0; i-- ) {
(function(i) {
if ( i == msgs.length - 1 ) {
msgs[i].next = function() { alert( 'done!' ); };
} else {
msgs[i].next = function() { handle_message( msgs[i + 1] ); };
}
})(i);
}
handle_message( msgs[0] );
Live demo: http://jsfiddle.net/simevidas/3CDdn/
Explanation:
The problem is with this function expression:
function() { handle_message( msgs[i + 1] ); }
This function has a live reference to the i variable. When this function is called, the for loop has long ended and the value of i is -1. If you want to capture the current value of i (the value during the iteration), you need to an additional wrapper function. This function captures the current value of i permanently (as an argument).
I think the problem is that i doesn't have the value you think it has:
// i is defined here:
for (var i=msgs.length-1; i>=0; i--)
{
if (i==msgs.length-1)
{
msgs[i].next = function() {alert('done!');};
}
else
{
msgs[i].next = function() {
// when this line gets executed, the outer loop is long finished
// thus i equals -1
handle_message(msgs[i+1]);
};
}
}
See point #5 Closures in loops at http://blog.tuenti.com/dev/top-13-javascript-mistakes/
Think about the values you are capturing in the closure.
msgs[i].next = function() {handle_message(msgs[i+1]);};
This captures the value of i, but it changes the next iteration so you get an infinite loop.
By the end of the loop i is -1 so i+1 is going just going to be the same message over and over again.