Introduction to javascript

Some details of this technique This technique uses window. Uses no global variables, and animation can be applied to any number of elements simultaneously The element is passed to animation function as an object and not with its ID. So it does not use ID's for the animated element, which makes it very comfortable to use; even tho the element can indeed be selected by its ID. The function started with window.

Introduction to javascript

It is simple and easy to read, but you wouldn't want to use it in most applications as it is blocking. This means that while you are reading the file from disk a slow operation nothing else can happen.

The simplest way to do this would be to use a callback. However, a naive implementation will probably go wrong: It doesn't work at all with control flow primitives.

It doesn't handle errors thrown by JSON. By the time we've done all of this our code is a mess of error handling: Promises help you naturally handle errors, and write cleaner code by not having callback parameters, and without modifying the Introduction to javascript architecture i.

What is a promise? The core idea behind promises is that a promise represents the result of an asynchronous operation. A promise is in one of three different states: Once a promise is fulfilled or rejected, it is immutable i. Constructing a promise Once all of the APIs return promises, it should be relatively rare that you need to construct one by hand.

In the meantime, we need a way to polyfill existing APIs. We give the constructor a factory function which does the actual work. This function is called immediately with two arguments.


The first argument fulfills the promise and the second argument rejects the promise. Once the operation has completed, we call the appropriate function.

Awaiting a promise In order to use a promise, we must somehow be able to wait for it to be fulfilled or rejected. The way to do this is using promise. With this in mind, it's easy to re-write our earlier readJSON function to use promises: Non Standard Note that promise. It is supported by most major promise libraries though, and is useful both as a teaching aid and in production code.

In our case, this second operation is synchronous, but it might just as easily have been an asynchronous operation. Fortunately, promises have a fully standardised, except jQuery method for transforming promises and chaining operations.

To put that another way, use. Now we can re-write our original example as simply: Fortunately, instead of using jQuery's strange version of a promise, you can just convert it to a really simple standardised promise: Browser Promises are currently only supported by a pretty small selection of browsers see kangax compatibility tables.

Instead, you're better off just requiring the library wherever you need it. To install promise run: MDN - The mozilla developer network has great documentation on promises.When designing an application that will communicate with a remote computer, a data format and exchange protocol must be selected.

There are a variety of open, standardized options, and the ideal choice depends on the applications requirements and pre . Learn JavaScript and Javascript arrays to build interactive websites and pages that adapt to every device.

Add dynamic behavior, store information, and handle requests and responses. This course can help marketers and designers upgrade their career and is a starting point for front-end engineers. This post is a part 18 of Advanced JavaScript APIs post series.

Introduction to javascript

In this article you will be learning all about JavaScript blobs. Every API in this post comes under HTML5 specification.

A blob object represents a chuck of bytes that holds data of a file. But a blob is not a reference to a actual file. touchstart Triggers when the user makes contact with the touch surface and creates a touch point inside the element the event is bound to. touchmove Triggers when the user moves the touch point across the touch surface.

touchend Triggers when the user removes a touch point from the surface. It fires. Furthermore, if you are using custom objects, you can set your own toJSON method which will be used by example.

Introduction to JavaScript is an online Computer Programming class at, that you can take at your own pace.

JavaScript - W3C DOM - Introduction