meteorhacks/zone.js

Name: zone.js

Owner: meteorhacks

Description: Implements Zones for JavaScript

Created: 2014-07-06 14:20:41.0

Updated: 2014-07-04 00:08:08.0

Pushed: 2014-06-12 19:03:35.0

Homepage: https://github.com/angular/zone.js

Size: 987

Language: null

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README

Zone.js

Build Status

Implements Zones for JavaScript, inspired by Dart.

What's a Zone?

A Zone is an execution context that persists across async tasks. You can think of it as thread-local storage for JavaScript VMs.

See this video from ng-conf 2014 for a detailed explanation:

screenshot of the zone.js presentation and ng-conf 2014

Running Within a Zone

You can run code within a zone with zone.run. Tasks scheduled (with setTimeout, setInterval, or event listeners) stay within that zone.

.run(function () {
ne.inTheZone = true;

tTimeout(function () {
console.log('in the zone: ' + !!zone.inTheZone);
 0);


ole.log('in the zone: ' + !!zone.inTheZone);

The above will log:

the zone: false'
the zone: true'

Note that the function delayed by setTimeout stays inside the zone.

Forking a Zone

Zones have a set of hooks that allow you to change the behavior of code running within that zone. To change a zone, you fork it to get a new one.

.fork({
foreTask: function () {
console.log('hi');

un(function () {
 do stuff

Hooks that you don't override when forking a zone are inherited from the existing one.

See the API docs below for more.

Usage

To start using Zones, you need to include the zone.js script in this package onto your page. This script should appear in the <head> of your HTML file before any other scripts, including shims/polyfills.

Examples

There are two kinds of examples:

  1. The kind you have to run
  2. Illustrative code snippets in this README
Running the ones that you have to run

For fully working examples:

  1. Spawn a webserver in the root of the directory in which this repo lives. (I like to use python -m SimpleHTTPServer 3000).
  2. Open http://localhost:3000/example in your browser

Below are the aforementioned snippets.

Tracking VM Turns

Run some function at the end of each VM turn:

.fork({
terTask: function () {
// do some cleanup

un(function () {
 do stuff
Overriding A Zone's Hook
someZone = zone.fork({
terTask: function () {
console.log('goodbye');



Zone.fork({
terTask: function () {
console.log('cya l8r');

un(function () {
 do stuff


ogs: cya l8r
Augmenting A Zone's Hook

When you fork a zone, you'll often want to control how the parent zone's hook gets called.

Prefixing a hook with $ means that the hook will be passed the parent zone's hook, and the hook will be expected to return the function to be invoked rather than be the function itself.

someZone = zone.fork({
terTask: function () {
console.log('goodbye');



Zone.fork({
fterTask: function (parentOnLeave) {
// return the hook
return function afterTask() {
  parentOnLeave();
  console.log('cya l8r');
};

un(function () {
 do stuff


ogs: goodbye
     cya l8r
+ and - Sugar

Most of the time, you'll want to run a hook before or after the parent's implementation. You can prefix a hook with - for running before, and + for running after.

The above can be written like this:

someZone = zone.fork({
terTask: function () {
console.log('goodbye');



Zone.fork({
afterTask': function (parentOnLeave) {
console.log('cya l8r');

un(function () {
 do stuff


ogs: goodbye
     cya l8r

This frees you from writing boilerplate to compose a new hook.

API

Zone.js exports a single object: window.zone.

zone.run

Runs a given function within the zone. Explained above.

zone.bind

Transforms a function to run within the given zone.

zone.fork
.fork({
foreTask: function () {},
terTask: function () {},
Error: function () {},
tTimeout: function () {},
tInterval: function () {},
ert: function () {},
ompt: function () {},
dEventListener: function () {}

ne.run(function () {
 woo!

Below describes the behavior of each of these hooks.

zone.onZoneCreated

Runs when a zone is forked.

zone.beforeTask

Before a function invoked with zone.run, this hook runs. If zone.beforeTask throws, the function passed to run will not be invoked.

zone.afterTask

After a function in a zone runs, the afterTask hook runs. This hook will run even if the function passed to run throws.

zone.onError

This hook is called when the function passed to run or the beforeTask hook throws.

zone.enqueueTask

This hook is called when a function is registered with the VM. For instance setTimeout and addEventListener.

zone.dequeueTask

This hook is called when a function is unregistered with the VM. For instance clearTimeout and removeEventListener.

zone.setTimeout, zone.setInterval, zone.alert, zone.prompt

These hooks allow you to change the behavior of window.setTimeout, window.setInterval, etc. While in this zone, calls to window.setTimeout will redirect to zone.setTimeout.

zone.addEventListener

This hook allows you to intercept calls to EventTarget.addEventListener.

Status
See also
License

Apache 2.0

This work is supported by the National Institutes of Health's National Center for Advancing Translational Sciences, Grant Number U24TR002306. This work is solely the responsibility of the creators and does not necessarily represent the official views of the National Institutes of Health.