Web API Cookbook

Preface

JavaScript has come a long way since its introduction in late 1995. In the early days, the core APIs built into web browsers were limited. More advanced functionality typically required third-party JavaScript libraries, or in some cases even browser plug-ins.

A web API is a series of global objects and functions exposed by the browser. Your JavaScript code can use these to interact with the Document Object Model (DOM), perform network communication, integrate with native device features, and much more.

Polyfills

Older browsers can take advantage of some of these APIs by using polyfills. A polyfill is a JavaScript library that implements missing functionality. Polyfills are typically used for web API features that aren’t implemented in older browsers.

While beneficial, polyfills do have some drawbacks:

• They are loaded as third-party libraries, which add to your bundle size.

• They generally aren’t maintained by the browser teams, so there may be bugs or inconsistencies.

• Some advanced functionality can’t be polyfilled in a performant way, or at all.

The Power of Modern Browsers

Modern web APIs have two big advantages for the web platform:

No more plug-ins

In the past, much of this functionality was only available to native applications or clunky browser plug-ins. (Remember ActiveX and Flash?)

Fewer third-party dependencies

Modern browsers provide considerable functionality that used to require third-party JavaScript libraries. Popular libraries such as jQuery, ...