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10 Useful Guidelines and Filters for AngularJS

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While working with AngularJS one often requires some guidelines and filters, which greatly simplify the development process and add responsiveness to interface. Many of them are quite trivial and demand access to search engines. Most of them can be found by a quick search, but I put together in one place a few tools that we commonly use in our project BitCalm .

Email address validation 

validateEmail: function (email) {
   var rx = /^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~-]+@[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$/;
   return rx.test(email);
To verify the email address we use a simple regular expression. Note that it is only used to verify that a user has not entered obvious nonsense. If you follow the RFC standard, it is possible to encounter some difficulties. This is due to various factors: the constant updating of the domain zones list, the use of Internationalized Domains (IDN), the use of sensitive addresses and many others. So, our validation  checks only the general structure of addresses (the presence of '@' and dot), otherwise it relies on the adequacy of a user. If you really want to validate  an email addresses, it is better to use a confirmation by e-mail than to come up with bulky regular expressions. 

Finding an element in the array by value

getByProperty: function (array, val, type) {
    var length = array.length;
    for (var i = 0; i < length; i++) {
        if (array[i][type] === val) {
            return a[i];
    return null;

The task of searching in an array by a value-specified field occurs quite often. For example, it can be used to find an element with a certain ID. The simplest function getByProperty eliminates the frequent use of cycles in a code.

Example of use:

user = getByProperty(usersArray, 1, 'id');

Generating a unique identifier

While developing single-page applications (SPA, single page applications), it is sometimes required  to create unique identifiers directly on the client side (front-end). For these identifiers to work properly with a server (back-end), you should create them in the usual UUID  format . Here is a small feature that has never let down:

generateUUID: function () {
    var s = [];
    var hexDigits = "0123456789abcdef";
    for (var i = 0; i < 36; i++) {
        s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
    s[14] = "4";
    s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1);
    s[8] = s[13] = s[18] = s[23] = "-";
    return s.join("");

Processing pressing Enter at input

To improve the experience of your product, it is worth thinking about even minor details. For example, you should allow a user to  still  operate with his usual hot keys. After filling some data in the text field I want to confirm the action by pressing Enter, instead  of taking your hands off the keyboard and drag the cursor to the button.

app.directive('ngEnter', [function () {
    return function (scope, element, attrs) {
        element.bind('keydown keypress', function (event) {
            if (event.which === 13) {
                scope.$apply(function (){

Here's how to use this directive:
<input type="text" ng-enter="action()"/>
<button ng-click="action()">Action!</button>

Representing bytes in a human-friendly format

Since BitCalm  commonly uses file sizes measurement, we needed a tool to convert units in a convenient format on the fly. For this purpose the following filter for Angular was written:

app.filter('bytes', function() {
    return function(bytes) {
        if (isNaN(parseFloat(bytes)) || !isFinite(bytes) || bytes == 0) return '0';

        var units = {1: 'KB', 2: 'MB', 3: 'GB', 4: 'TB'},
            measure, floor, precision;

        if (bytes > 1099511627775) {
            measure = 4;
        } else if (bytes > 1048575999 && bytes <= 1099511627775) {
            measure = 3;
        } else if (bytes > 1024000 && bytes <= 1048575999) {
            measure = 2;
        } else if (bytes <= 1024000) {
            measure = 1;

        floor = Math.floor(bytes / Math.pow(1024, measure)).toString().length;
        if (floor > 3) {
            precision = 0
        } else {
            precision = 3 - floor;
        return (bytes / Math.pow(1024, measure)).toFixed(precision) + units[measure];

Here's how it works:

<span>{{ 234242345 | bytes }}</span> <!-- '223MB' -->
<span>{{ 56734654 | bytes }}</span>  <!-- '54.1MB' -->
<span>{{ 1024 | bytes }}</span>      <!-- '1.00KB' -->

Creating a nested scrolling

The situation where on the page with a scroll bar there is sub-element, which you can also scroll through, causes great inconvenience.


When the cursor is over an area 2, both scroll bars will be scrolled which makes it impossible to comfortably view the content in this area. To solve this problem, we use a simple directive:

app.directive('nestedScroll', [function () {
    return function (scope, element) {
        element.on('mousewheel DOMMouseScroll', function (e) {
            var e0 = e.originalEvent || e,
                delta = e0.wheelDelta || -e0.detail;

            this.scrollTop += ( delta < 0 ? 1 : -1 ) * 30;

When you hover over the necessary item the standard action gets blocked  and a simple operation is applied with the scrollTop feature.

Playing sound upon certain events

If your application requires producing sound upon specific events, it can be done with the help of the following directives:

app.directive('soundNotification', [function () {
    return function (scope, element, attrs) {
        scope.$on('playSound', function () {
            element.attr('src', '');
            element.attr('src', attrs.msrc);

Now, of all the places of an application you can send 'playSound' events using $emit and $broadcast. The element must have the attribute 'msrc' with the path to a file. Otherwise, the path can be sent to an event as an argument.

Determining of the tab browser activity

There are times for you to perform some action when the user switched from the tab with your application (the examples of actions are switching on audio alerts, enable browser-based notification, etc.). For this one may use the following function:

detectTabActivity: function (focusInCallback, focusOutCallback) {
    var notIE = (document.documentMode === undefined);

    if (notIE && !window.chrome) {
        $(window).on("focusin", focusInCallback).on("focusout", focusOutCallback);
    } else {
        if (window.addEventListener) {
            window.addEventListener("focus", focusInCallback, false);
            window.addEventListener("blur", focusOutCallback, false);
        } else {
            window.attachEvent("focus", focusInCallback);
            window.attachEvent("blur", focusOutCallback);

Two callback-functions, which come for an input, can perform any action upon the 'focus' or 'blur' events.

I hope this method will be as useful for your AngularJS work as it was for ours .

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