JavaScript and UI Architecture Best Practices

JavaScript and UI Architecture Best Practices Siarhei Barysiuk s.barysiuk@sam-solutions.net

Our roadmap

Introduction: What will we cover today? • Coding patterns JavaScript-speciﬁc best practices • Design patterns Language independent patterns, UI architecture

Coding patterns

Namespaces

Tip of the day “Global variables should be avoided in order to lower the possibility of variable naming collisions. “

Namespaces: Deﬁning namespace //defining top-level package var MyApp = MyApp || {}; //defining package //defining package MyApp.dom = { MyApp.string = MyApp.string || {}; addEventListener: function(element, //defining package callback) { MyApp.string.utils = { //code goes here trim: function(str) { }, //code goes here removeEventListener: function(element, }, callback) { reverse: function(str) { //code goes here //code goes here } } }; };

Namespaces: Usage in code MyApp.string.utils.reverse(...); MyApp.string.utils.trim(...); MyApp.dom.addEventListener(...); MyApp.dom.removeEventListener(...);

Namespaces: namespace() function //defining top-level package var MyApp = MyApp || {}; //defines package structure MyApp.namespace = function(name) { if(name) { //some checks if name is valid var names = name.split(quot;.quot;); var current = MyApp; for(var i in names) { if(!current[names[i]]) { current[names[i]] = {}; } current = current[names[i]]; } return true; } return false; };

Namespaces: Deﬁning namespace //defining top-level package var MyApp = MyApp || {}; //defining package //defining package MyApp.string = MyApp.string || {}; MyApp.namespace(quot;string.utilsquot;); //defining package //defining package MyApp.string.utils = { MyApp.string.utils.trim = function(str) { trim: function(str) { //code goes here //code goes here console.log(quot;trimquot;); }, }; reverse: function(str) { //code goes here MyApp.string.utils.reverse = function(str) { } //code goes here }; console.log(quot;reversequot;); };

Questions?

Init-time branching

Tip of the day “Branch some parts of the browser-speciﬁc code during initialization, when the script loads, rather than during runtime to avoid performance hit.”

Init-time branching: Deﬁning browser-speciﬁc methods MyApp.namespace(quot;domquot;); MyApp.dom.addListener = null; //all major browsers if(typeof window.addEventListener === 'function') { MyApp.dom.addListener = function(el, type, fn) { el.addEventListener(type, fn, false); }; } //IE else if(typeof document.attachEvent === 'function') { MyApp.dom.addListener = function(el, type, fn) { el.attachEvent('on' + type, fn); }; } //older browsers else { MyApp.dom.addListener = function(el, type, fn) { el['on' + type] = fn; }; }

Questions?

Lazy deﬁnition

Tip of the day “The lazy deﬁnition pattern is very similar to the previous init-time branching pattern. The difference is that the branching happens only when the function is called for the ﬁrst time.”

Lazy definition: Defining browser-specific methods var MyApp = MyApp || {}; Override function first time MyApp.dom = { addListener: function(el, type, fn){ if (typeof el.addEventListener === 'function') { MyApp.dom.addListener = function(el, type, fn) { el.addEventListener(type, fn, false); }; } else if (typeof el.attachEvent === 'function'){ MyApp.dom.addListener = function(el, type, fn) { el.attachEvent('on' + type, fn); }; } else { MyApp.dom.addListener = function(el, type, fn) { el['on' + type] = fn; }; } MyApp.dom.addListener(el, type, fn); } };

Questions?

Conﬁguration object

Tip of the day “Instead of having many parameters, you can use one parameter and make it an object. The properties of the object are the actual parameters.”

Conﬁguration object: Ordinary constructor var MyApp = MyApp || {}; MyApp.namespace(quot;domquot;); MyApp.dom.Button = function(text, type) { //some code here } MyApp.dom.Button = function(text, type, color, border, font) { //some code here }

Conﬁguration object: Usage of conﬁguration object var MyApp = MyApp || {}; MyApp.namespace(quot;domquot;); MyApp.dom.Button = function(text, settings) { var type = settings.type || 'submit'; var font =settings.font ||'Verdana'; //..other props //some code here }

Questions?

Private properties and methods

Tip of the day “Use local variables and methods inside a constructor to achieve the “private” level of protection. Use naming conventions _doInternalOperation to show that the function is private/protected.”

Private methods and properties: Private method var MyApp = MyApp || {}; MyApp.namespace(quot;domquot;); MyApp.dom.Button = function(text, settings) { //..process properties function setStyle(element, settings) { //setting style to element }; var button = //... //.. setStyle(button,settings); this.clone = function() { var clonedButton = //... //... setStyle(clonedButton, settings); } //some code here }

Questions?

Self-executing functions

Tip of the day “Self-executing functions are especially suitable for one-off initialization tasks performed when the script loads.”

Self-executing functions: Usage (function() { //code goes here })(); (function(){ // ... var jQuery = window.jQuery = window.$ = function( selector, context ) { // ... return new jQuery.fn.init( selector, context ); }; // ... jQuery.fn = jQuery.prototype = { init: function() { //... } }; })();

Questions?

Chaining

Tip of the day “Pretty convenient way to call several related methods on one line as if the methods are the links in a chain.”

Chaining: Usage var obj = new MyApp.dom.Element('span'); var obj = new MyApp.dom.Element('span'); obj.setText('hello'); obj.setText('hello') obj.setStyle('color', 'red'); .setStyle('color', 'red') obj.setStyle('font', 'Verdana'); .setStyle('font', 'Verdana'); document.body.appendChild(obj); document.body.appendChild(obj); document.body.appendChild( new MyApp.dom.Element('span') .setText('hello') .setStyle('color', 'red') .setStyle('font', 'Verdana') );

Questions?

Design patterns

Unobtrusive JavaScript

Unobtrusive JavaScript: Separate JavaScript functionality <a onclick=quot;doSomething()quot; href=quot;#quot;>Click!</a> <a href=quot;backuplink.htmlquot; class=quot;doSomethingquot;>Click!</a> $('a.doSomething').click(function(){ // Do something here! alert('You did something, woo hoo!'); });

Unobtrusive JavaScript: Never depend on JavaScript <script type=quot;text/javascriptquot;> var now = new Date(); if(now.getHours() < 12) document.write('Good Morning!'); else document.write('Good Afternoon!'); </script> <p title=quot;Good Day Messagequot;>Good Morning!</p> var now = new Date(); if(now.getHours() >= 12) { var goodDay = $('p[title=quot;Good Day Messagequot;]'); goodDay.text('Good Afternoon!'); }

Unobtrusive JavaScript: Never depend on JavaScript <a href=quot;javascript:window.open('page.html')quot;>my page</a> <a href=quot;#quot; onclick=quot;window.open('page.html')quot;>my page</a> <a href=quot;page.htmlquot; onclick=quot;window.open(this.href)quot;>my page</a> <a href=quot;page.htmlquot; class=quot;popupquot;>my page</a> //some java script to open element with class quot;.popupquot; in a new window

Questions?

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JavaScript and UI Architecture Best Practices

by Siarhei Barysiuk

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