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Observer

An asynchronous observer that batches updates per subject and callback.

Import
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import { Observer } from "@schukai/monster/source/types/observer.mjs";
Source
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Package
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Since
1.0.0

Observer is the asynchronous callback primitive behind Monster's observable structures. It batches updates per subject inside one microtask cycle so duplicate triggers collapse into one execution.

Use it when update notifications should stay cheap and consistent even if a subject changes several times in quick succession.

/** this example does not use an extra script **/
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Schedule A Deduplicated Observer Update

import { Observer } from "@schukai/monster/source/types/observer.mjs";

const output = document.getElementById("observer-output");
let runs = 0;

const observer = new Observer(function () {
    runs += 1;
    output.textContent = `runs: ${runs}`;
});

document.getElementById("observer-run").addEventListener("click", async () => {
    runs = 0;
    output.textContent = "scheduled";
    const subject = { name: "demo" };
    await Promise.all([observer.update(subject), observer.update(subject)]);
});
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Exported

Observer

Derived from

Base

Options

The Options listed in this section are defined directly within the class. This class is derived from several parent classes. Therefore, it inherits Options from these parent classes. If you cannot find a specific Options in this list, we recommend consulting the documentation of the Base.

Option
Type
Default
Description
-/-

Properties

The Properties listed in this section are defined directly within the class. This class is derived from several parent classes. Therefore, it inherits Properties from these parent classes. If you cannot find a specific Properties in this list, we recommend consulting the documentation of the Base.

Methods

The methods listed in this section are defined directly within the class. This class is derived from several parent classes. Therefore, it inherits methods from these parent classes. If you cannot find a specific method in this list, we recommend consulting the documentation of the Base.

Constructor

constructor(callback,args)
Parameters
  • callback {function}: The function to execute on update.
  • args {...*}: Additional arguments to pass to the callback.

Behavioral methods

addTag(tag)
Parameters
  • tag {string}: tag
removeTag(tag)
Parameters
  • tag {string}: tag
update(subject)
Parameters
  • subject {object}: The subject object that triggered the update.
Schedules the callback for execution with the given subject. If multiple updates for the same subject are requested in the same event loop tick, the callback is only executed once. All callers will receive the same promise. or rejects if the callback throws an error.

State query methods

hasTag(tag)
Parameters
  • tag {string}: tag

Structural methods

getTags()

Static methods

[instanceSymbol]()2.1.0
This method is called by the instanceof operator.

Other methods

arguments()
Getter for properties for cleaner access if needed
callback()
Getter for properties for cleaner access if needed

Events

This component does not fire any public events. It may fire events that are inherited from its parent classes.

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