Book Image

Javascript Unlocked

Book Image

Javascript Unlocked

Overview of this book

JavaScript stands bestride the world like a colossus. Having conquered web development, it now advances into new areas such as server scripting, desktop and mobile development, game scripting, and more. One of the most essential languages for any modern developer, the fully-engaged JavaScript programmer need to know the tricks, non-documented features, quirks, and best practices of this powerful, adaptive language. This all-practical guide is stuffed with code recipes and keys to help you unlock the full potential of JavaScript. Start by diving right into the core of JavaScript, with power user techniques for getting better maintainability and performance from the basic building blocks of your code. Get to grips with modular programming to bring real power to the browser, master client-side JavaScript scripting without jQuery or other frameworks, and discover the full potential of asynchronous coding. Do great things with HTML5 APIs, including building your first web component, tackle the essential requirements of writing large-scale applications, and optimize JavaScript’s performance behind the browser. Wrap up with in-depth advice and best practice for debugging and keeping your JavaScript maintainable for scaling, long-term projects. With every task demonstrated in both classic ES5 JavaScript and next generation ES6-7 versions of the language, Whether read cover-to-cover or dipped into for specific keys and recipes, JavaScript Unlocked is your essential guide for pushing JavaScript to its limits.
Table of Contents (15 chapters)
JavaScript Unlocked
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Tuning performance


Performance makes user experience. If it takes too long to load a page or a UI to respond, the user is likely to leave the application and never come back. It's especially true with web apps. In Chapter 3, DOM Scripting and AJAX, we compared different approaches to manipulate the DOM. In order to find out how fast an approach is, we use a performance built-in object:

"use strict";
var cpuExpensiveOperation = function(){
      var i = 100000;
      while( --i ) {
        document.body.appendChild( document.createElement( "div" ) );
      }
    },
    // Start test time
    s = performance.now();

cpuExpensiveOperation();
console.log( "Process took", performance.now() - s, "ms" );

performance.now() returns a high resolution timestamp that represents time in milliseconds accurate to microseconds. This is designed and widely used for benchmarking. However, a time/timeEnd console object also provides methods to measure time:

console.time( "cpuExpensiveOperation took" );
cpuExpensiveOperation...