jquery-placeholder is a simple jQuery plugin that enables form placeholders in browsers that do not support them natively, i.e. IE < 10.

Properties

• Works in IE6.
• Automatically checks whether the browser natively supports the HTML5 placeholder attribute for input and textarea elements. If this is the case, the plugin won’t do anything. If @placeholder is only supported for input elements, the plugin will leave those alone and apply to textareas exclusively. (This is the case for Safari 4, Opera 11.00, and possibly other browsers.)
  ...

Rails comes with a Rake task notes that shows code comments that start with "TODO", "FIXME", or "OPTIMIZE".

While it's generally not good practice to leave them in your code (your work is not done until it's done), in larger projects you will occasionally have to use them as other parts of the application that you depend upon are not yet available.
To keep track of them, run rake notes. Its output looks something like this:

$ rake notes
app/controllers/fron...

When ending a Selenium test Capybara resets the browser state by closing the tab, clearing cookies, localStorage, etc.

It may be a good idea to wait for all in-flight AJAX requests to finish before ending a scenario:

• You may have client-side JavaScript that freaks out when the tab closure kills their pending requests. If that JavaScript opens an error alert or spams errors to the console, your test may fail after the last step.
• With unlucky timing the server may receive an AJAX request as the browser tab closes, causing a connection ...

Reason

If you are using Coffeescript, it is likely to be the culprit. Since Coffeescript always returns the value of the last expression, it may return DOM nodes:

# coffeescript
scope.focus = ->
  element.focus()

# javascript
scope.focus = function() {
  return element.focus(); // wheee
}

If you e.g. use this function like this, the error will be raised:

<span ng-click="focus()">...</span>

Solution

By adding an explicit return value (e.g. return false), you can Coffees...

Please don't simply copy line number links from Github. The URL usually contains a branch name like master which will change over time:

https://github.com/makandra/upjs/blob/master/lib/assets/javascripts/up/link.js.coffee#L76

If someone now posts an insertion or deletion to that file into master your link points to the wrong line!

A better way is to press the Y key after clicking on a line number. This will transform the URL to another URL that points to the particular commit:

https://github.com/makandra/upjs/blob/b3b14...

Webfonts are not always available when your JavaScript runs on first page load. Since fonts may affect element sizes, you may want to know when fonts have been loaded to trigger some kind of recalculation.

Vanilla JavaScript / Modern DOM API

In modern browsers (all but IE and legacy Edge) you can use document.fonts. Use load to request a font and receive a Promise that will be resolved once the font is available. Example:

document.fonts.load('1rem "Open S...

jQuery doesn't store information about event listeners and data values with the element itself. This information is instead stored in a global, internal jQuery cache object. Every time you add an event listener or data value to a jQuery object, the jQuery cache gains another entry.

The only way that a jQuery cache entry gets deleted is when you call remove() on the element that put it there!

Since cache entries also have a pointer back to the element that spawned them, it is easy to create DOM elements that can never be garbage-co...

This guide shows how to create an AngularJS application that consumes more and more memory until, eventually, the browser process crashes on your users.

Although this guide has been written for Angular 1 originally, most of the advice is relevant for all client-side JavaScript code.

How to observe memory consumption

To inspect the amount of memory consumed by your Javascripts in Chrome:

• Open an incognito window
• Open the page you want to inspect
• Press Shift + ESC to see a list of Chrome processes...

The easiest way to detect touch-capable browsers is to check for the presence of touch events. It is no 100% solution, but has by far the best cost-benefit ratio. (Know that this does not detect touch devices, but browsers.)

Javascript

var isTouchDevice = 'ontouchstart' in window

Coffeescript

isTouchDevice = 'ontouchstart' of window

On the difference between the Javascript and the Coffeescript version, see [Beware: Coffeescript "in" is not the Javascript "in"](https://makandracards.com/makandra/31073-beware-c...

The Javascript in operator does what Hash#has_key? does in Ruby: Return whether an object has a property.
However, Coffeescript has its own in operator that checks for array inclusion. To check whether an object has a property, use of:

Javascript

'name' in {name: 'Horst'} # => true

Coffeescript

# wrong
'name' in {name: 'Horst'} # => false

# correct
'name' of {name: 'Horst'} # => true
1 in [1,2,3] # => true

True story.

When testing code that uses pushState / replaceState, your browser will appear to navigate away from http://localhost:3000/specs (or wherever you run your Jasmine tests). This is inconvenient, since reloading the document will no longer re-run the test suite.

To remedy this, copy the attached file to a place like spec/javascripts/helpers and #= require it from your tests. It will store the current location before every test and reset if afterwards (using location.replaceState).

This jasmine plugin helps with testing DOM manipulation in two ways:

1. It gives you DOM-related matchers like toBeVisible() or toHaveCss(css)
2. It gives you a function to load HTML from fixture files. Without this you would have to manually add elements to <body> and clean up afterwards.

When running Selenium features with parallel_tests, some browser-server interaction might take longer than usual and the impatient Capybara will not wait enough to see results.

Put the attached file into features/support/ to make Capybara more patient in scenarios tagged @javascript.

Build dashboards using ascii/ansi art and javascript

Awesome!

Angular 1.3+ has an alternative getter/setter pattern: You can bind ng-model to an accessor function. This is a function that is either a getter (when it gets no arguments) or a setter (when it gets the new value as an argument):

$scope.name = function(newName) {
  return angular.isDefined(newName) ? (_name = newName) : _name;
}

You need to bind this function with ng-model and `ng-model-options="{ getterSette...

JavaScript objects can have getter and setter functions that are called when a property is read from or written to.

For example, if you'd like an object that has a virtual person.fullName attribute that dynamically composes person.firstName and person.lastName:

var person = {

  firstName: 'Guybrush',

  lastName: 'Threepwood',

  get fullName() {
    return this.firstName + " " + this.lastName;
  },
  
  set fullName(name) {
    var parts = name.split(" ");
    this.firstName = parts[0];
    this.lastName = parts[1];
  }

};
`...

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...

Responsive Lightbox JavaScript that just works.

You can use it for single images or a gallery. Animations are optional.

The API is a little confusing because animate returns a reference to the element to enable chaining.
But you can do this:

$element.animate(...);
$element.promise().then(function() { ... });

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...

You can do so much more than console.log(...)! See the attached link for a great breakdown of what the developer console can give you.

Some of my favorites:

console.log takes many arguments

E.g. console.log("Current string:", string, "Current number:", 12)

Your output can have hyperlinks to Javascript objects

E.g. console.log("Check out the current %o, it's great", location)

[Di...

Databound provides Javascript a simple API to the Ruby on Rails CRUD.

Tries to expose a full model CRUD as an API. Not sure if this is useful for more refined requirements.

A set of javascript tools for working with files.

It offers different kinds of things:

• A cross-browser JS API to work with File objects.
• Image helper methods, like rotating images, or generating thumbnails in the browser (because you don't want your browser to scale tons of 20MB-JPEGs just for an upload preview)
• Webcam access
• Uploads

When HTML5 support is unavailable, it uses Flash polyfills.

Check out the documentation and demos at their GitHub page.

To install via bower, simply add the `...