Sometimes modern Javascript projects get out of hand. A major culprit in this can be the messy handling of asynchronous tasks, leading to long, complex, and deeply nested blocks of code. Javascript now provides a new syntax for handling these operations, and it can turn even the most convoluted asynchronous operations into concise and highly readable code.

ChromeDriver clicking works by simulating a mouse click in the middle of the element's first client rect (or bounding client rect if it doesn't have a first client rect). (Clicking issues)

So if you are trying to click on an element, chromedriver tries to click at the position where it first finds that element.

This can lead to some problems and unexpected behavior like:

• Element is not clickable at point ... erros
• Another element which is now located at...

Some modern Javascript APIs return iterators instead of arrays.

In plain Javascript you can loop through an iterator using
for...of:

var iterator = ...;

for (var value of iterator) {
   console.log(value); 
}

While there is a for...of construct in Coffeescript, it iterates through property/value pairs and **...

Until recently, you could open a new tab via window.open when using execute_script in Selenium tests. It no longer works in Chrome (will show a "popup blocked" notification).

This is because browsers usually block window.open unless the user interacted with an element for security reasons. I am not sure why it did work via Selenium before.

Here is an approach that will insert a link into the page, and have Selenium click it:

path = "/your/path/here"
id = "helper_#{SecureRandom.hex(8)}"
execute_script <<-JAVASCRIPT
  ...

What's new

• Moved from Less to Sass. Bootstrap now compiles faster than ever thanks to Libsass, and we join an increasingly large community of Sass developers.
• Improved grid system. We’ve added a new grid tier to better target mobile devices and completely overhauled our semantic mixins.
  Opt-in flexbox support is here. The future is now—switch a boolean variable and recompile your CSS to take advantage of a flexbox-based grid system and components.
• Dropped wells, thumbnails, and panels for cards. Cards are a brand new co...

Unfortunately, Web APIs haven’t provided the functionality to copy text to the clipboard through JavaScript, which is why visiting GitHub with Flash disabled shows an ugly grey box where the button is supposed to be. Fortunately, we have a solution. The editor APIs provide document.execCommand as an entry point for executing editor commands. The "copy" and cut" commands have previously been disabled for web pages, but with Firefox 41, which is currently in Beta, and slated to move to release in mid-September, it is becoming available to Ja...

This is a problem when using Selenium with Firefox. We recommend using ChromeDriver for your Selenium tests.

This setup allows to test focus/blur events in Cucumber tests (using Selenium). For background information, see How to solve Selenium focus issues.

Cucumber step definition:

# This step is needed because in Selenium tests, blur events are not triggered
# when the browser has no focus.
When /^I unfocus the "(.*?)" field to trigger ja...

jQuery comes with .animate() that lets you transition some CSS selectors:

function floatIn($element) {
  $element.css({ 'opacity': 0, 'margin-top': 200px });
  $element.animate({ 'opacity': 1, 'margin-top': 0 }, { duration: 500 });
}

The animation is implemented using setInterval and Javascript. This works great, but it's not as smooth as a CSS transition.

Fortunately the animate API can be mapped almo...

Javascript library for drag'n'drop that seems to have more options than native HTML5 drag'n'drop.

They also claim to support "multi-touch", which would be awesome if it means that you can drag on touch devices.

Another library with similar aims is interact.js (Github).

They're pitching JavaScript drag and drop, resizing and multi-touch gestures with inertia and snapping for modern browsers (and also IE8+).

Amazing guide how to divide a ball of Javascript spaghetti distinct separate layers (model, view, controller, backend adapter).

It does not use a Javascript framework.

When you are working with Backbone models and inheritance, at some point you want to overwrite inherited methods but call the parent's implementation, too.
In JavaScript, there is no simple "super" method like in Ruby -- so here is how to do it with Backbone.

Example

BaseClass = Backbone.Model.extend({
  initialize: function(options) {
    console.log(options.baseInfo);
  }
});

MyClass = BaseClass.extend({
  initialize: function(options) {
    console.log(options.myInfo);
  }
});

ne...

A tooltip library that does not use Javascript. Works in IE9+.

This library (or the technique used by it) could be a great choice for projects with a lot of tooltips, which are hard to do fast with Javascript.

Turbolinks makes following links in your web application faster. Instead of letting the browser recompile the JavaScript and CSS between each page change, it keeps the current page instance alive and replaces only the body and the title in the head.

This is similar to pjax, but instead of worrying about what element on the page to replace, and tailoring the server-side response to fit, we replace the entire body. This means that you get the bulk of the speed benefits from pjax (no recompiling of the JavaScript or CSS) without having to tail...

For my Gem Session project Holly I ran the Ironman of drag'n'drop implementations:

• Dragging in nested lists
• User-definable order of items
• Complicated item elements with super-custom CSS and other Javascript functionality
• Items that can be both leaves and containers of other items
• has_ancestry on the server side

Things I learned:

• Be ready to write a lot of CSS. You need to indicate what is being dragged, where it will be dropped, if it is dropped above, below o...

This is a demo of the "Tabby" Javascript jQuery plugin to use tabs in regular textareas to make them suitable for in-browser coding of languages like HTML, CSS, Javascript, or your favorite server-side language. The idea is to be able to use a press of the TAB button or SHIFT+TAB to indent or outdent your code.

In Rails 2, you could use link_to_remote ... :update => 'id' to automatically replace the content of $('#id').

To do the same in Rails 3, include usual rails-ujs JavaScript, and put this into your application.js:

$(function() {
  $('[data-remote][data-replace]')
    .data('type', 'html')
    .live('ajax:success', function(event, data) {
      var $this = $(this);
      $($this.data('replace')).html(data);
      $this.trigger('ajax:replaced');...

If you manipulate the DOM with JavaScript and your page contains nested elements with position: relative, chances are Internet Explorer 7 will not properly move to the right position.

I have not found a fool-proof workaround, but these are options that have worked for me:

• Try to lose some position: relative attributes, so they do not nest. This is often impossible, though.
• Force the correct redrawing of the elements using JavaScript. Adding a bogus class ($(element).addClass('touch')) seems to suffice.
• Try to give the off...

Cucumber scenarios that are tagged with @javascript so they run with Selenium are very slow. You might not want to run them every time.

In order to skip all Selenium scenarios, call Cucumber like this:

cucumber --tags ~@javascript

Note that you should still run all the scenarios, including the Selenium ones, before you push a change.

You can use these step definitions:

Then /^I should not see an error$/ do
  (200 .. 399).should include(page.status_code)
end

Then /^I should see an error$/ do
  (400 .. 599).should include(page.status_code)
end

Note that you need to tag the scenario with @allow-rescue to test that an error is shown like this

@allow-rescue
Scenario: Accessing the admin area requires a login
  When I go to the admin area
  Then I should see an error

These step definitions will not work for @javascript scena...

Currently not possible as the linked .htc file contains JavaScript which is not explicitly called.

The developers are working on a pure JavaScript solution which will have some downsides but work across different domains.

Capybara sets up some tags for you to use in Cucumber. Often you’ll want to run only some scenarios with a driver that supports JavaScript, Capybara makes this easy: simply tag the scenario (or feature) with @javascript:

When a Ruby version gem has a letter in its version number, it is considered a pre-release:

• 1.0.0.rc1
• 2.3.0.alpha2
• 3.0.0.beta3
• 4.0.0.pre.rc2

Even if a pre-release gem has the highest version number, it is never installed unless the user explictily requested the version:

gem install foobar --version="=2.3.0.alpha2"

Also bundle update will never update a stable version to a pre-release version unless the user explicitly requests it in the Gemfile:

gem 'foobar', '=2.3.0.alpha2'

A note on Semanti...