Zone.js
Implements Zones for JavaScript.
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.
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.
zone.run(function () {
zone.inTheZone = true;
setTimeout(function () {
console.log('in the zone: ' + !!zone.inTheZone);
}, 0);
});
console.log('in the zone: ' + !!zone.inTheZone);
The above will log:
'in the zone: false'
'in 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.
zone.fork({
onZoneEnter: function () {
console.log('hi');
}
}).run(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.
Examples
There are two kinds of examples:
- The kind you have to run
- Illustrative code snippets in this README
Running the ones that you have to run
For fully working examples:
- Spawn a webserver in the root of the directory in which this repo lives.
(I like to use
python -m SimpleHTTPServer 3000
). - 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:
zone.fork({
onZoneLeave: function () {
// do some cleanup
}
}).run(function () {
// do stuff
});
Overriding A Zone's Hook
var someZone = zone.fork({
onZoneLeave: function () {
console.log('goodbye');
}
});
someZone.fork({
onZoneLeave: function () {
console.log('cya l8r');
}
}).run(function () {
// do stuff
});
// logs: cya l8r
Augmenting A Zone's Hook
var someZone = zone.fork({
onZoneLeave: function () {
console.log('goodbye');
}
});
someZone.fork({
onZoneLeave: function () {
this.parent.onZoneLeave();
console.log('cya l8r');
}
}).run(function () {
// do stuff
});
// logs: goodbye
// cya l8r
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
zone.fork({
onZoneEnter: function () {},
onZoneLeave: function () {},
onError: function () {},
setTimeout: function () {},
setInterval: function () {},
alert: function () {},
prompt: function () {},
addEventListener: function () {}
});
myZone.run(function () {
// woo!
});
Below describes the behavior of each of these hooks.
zone.onZoneEnter
Before a function invoked with zone.run
, this hook runs.
If zone.onZoneEnter
throws, the function passed to run
will not be invoked.
zone.onZoneLeave
After a function in a zone runs, the onZoneLeave
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 onZoneEnter
hook throws.
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
setTimeout
,setInterval
, andaddEventListener
work in FF23, IE10, and Chrome.- stack trace rewrite is kinda ugly and may contain extraneous calls.
elt.onevent
works in FF23, IE10, but not Chrome. There's a fix in the works though!
License
Apache 2.0