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can-define

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Exports the define method that defines observable properties and their behavior on a prototype object.

define(prototype, propDefinitions)

Define observable properties, type conversion, and getter/setter logic on prototype objects.

import define from "can-define";

const Greeting = function( message ) {
    this.message = message;
};

define( Greeting.prototype, {
    message: { type: "string" }
} );

Parameters

  1. prototype {Object}:

    The prototype object of a constructor function or class. The prototype object will have getter/setters defined on it that carry out the defined behavior. The prototype will also contain all of can-event-queue/map/map's methods.

  2. propDefinitions {Object<String,PropDefinition>}:

    An object of properties and their definitions.

Use

can-define provides a way to create custom types with observable properties. Where can-define/map/map and can-define/list/list provide more functionality, they also make more assumptions on the type constructor. can-define can be used to create completely customized types.

The following creates a Person constructor function:

import define from "can-define";

const Person = function( first, last ) {
    this.first = first;
    this.last = last;
};
define( Person.prototype, {
    first: { type: "string" },
    last: { type: "string" },
    fullName: {
        get: function() {
            return this.first + " " + this.last;
        }
    }
} );

This can be used to create Person instances with observable properties:

const person = new Person( "Justin", "Meyer" );
person.first;    //-> "Justin"
person.last;     //-> "Meyer"
person.fullName; //-> "Justin Meyer"

person.on( "fullName", function( ev, newVal, oldVal ) {
    newVal; //-> "Ramiya Meyer"
    oldVal; //-> "Justin Meyer"
} );

person.first = "Ramiya";

The observable properties call ObservationRecorder.add so they can be observed by can-compute.

CanJS is part of DoneJS. Created and maintained by the core DoneJS team and Bitovi. Currently 4.3.0.

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