/**
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* @license
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* Knockout ES5 plugin - https://github.com/SteveSanderson/knockout-es5
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* Copyright (c) Steve Sanderson
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* MIT license
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*/
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var OBSERVABLES_PROPERTY = '__knockoutObservables';
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var SUBSCRIBABLE_PROPERTY = '__knockoutSubscribable';
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// Model tracking
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// --------------
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//
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// This is the central feature of Knockout-ES5. We augment model objects by converting properties
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// into ES5 getter/setter pairs that read/write an underlying Knockout observable. This means you can
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// use plain JavaScript syntax to read/write the property while still getting the full benefits of
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// Knockout's automatic dependency detection and notification triggering.
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//
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// For comparison, here's Knockout ES3-compatible syntax:
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//
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// var firstNameLength = myModel.user().firstName().length; // Read
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// myModel.user().firstName('Bert'); // Write
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//
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// ... versus Knockout-ES5 syntax:
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//
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// var firstNameLength = myModel.user.firstName.length; // Read
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// myModel.user.firstName = 'Bert'; // Write
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// `ko.track(model)` converts each property on the given model object into a getter/setter pair that
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// wraps a Knockout observable. Optionally specify an array of property names to wrap; otherwise we
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// wrap all properties. If any of the properties are already observables, we replace them with
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// ES5 getter/setter pairs that wrap your original observable instances. In the case of readonly
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// ko.computed properties, we simply do not define a setter (so attempted writes will be ignored,
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// which is how ES5 readonly properties normally behave).
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//
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// By design, this does *not* recursively walk child object properties, because making literally
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// everything everywhere independently observable is usually unhelpful. When you do want to track
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// child object properties independently, define your own class for those child objects and put
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// a separate ko.track call into its constructor --- this gives you far more control.
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function track(obj, propertyNames) {
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if (!obj /*|| typeof obj !== 'object'*/) {
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throw new Error('When calling ko.track, you must pass an object as the first parameter.');
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}
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var ko = this,
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allObservablesForObject = getAllObservablesForObject(obj, true);
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propertyNames = propertyNames || Object.getOwnPropertyNames(obj);
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propertyNames.forEach(function(propertyName) {
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// Skip storage properties
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if (propertyName === OBSERVABLES_PROPERTY || propertyName === SUBSCRIBABLE_PROPERTY) {
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return;
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}
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// Skip properties that are already tracked
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if (propertyName in allObservablesForObject) {
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return;
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}
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var origValue = obj[propertyName],
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isArray = origValue instanceof Array,
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observable = ko.isObservable(origValue) ? origValue
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: isArray ? ko.observableArray(origValue)
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: ko.observable(origValue);
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Object.defineProperty(obj, propertyName, {
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configurable: true,
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enumerable: true,
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get: observable,
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set: ko.isWriteableObservable(observable) ? observable : undefined
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});
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allObservablesForObject[propertyName] = observable;
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if (isArray) {
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notifyWhenPresentOrFutureArrayValuesMutate(ko, observable);
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}
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});
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return obj;
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}
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// Gets or creates the hidden internal key-value collection of observables corresponding to
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// properties on the model object.
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function getAllObservablesForObject(obj, createIfNotDefined) {
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var result = obj[OBSERVABLES_PROPERTY];
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if (!result && createIfNotDefined) {
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result = {};
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Object.defineProperty(obj, OBSERVABLES_PROPERTY, {
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value : result
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});
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}
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return result;
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}
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// Computed properties
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// -------------------
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//
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// The preceding code is already sufficient to upgrade ko.computed model properties to ES5
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// getter/setter pairs (or in the case of readonly ko.computed properties, just a getter).
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// These then behave like a regular property with a getter function, except they are smarter:
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// your evaluator is only invoked when one of its dependencies changes. The result is cached
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// and used for all evaluations until the next time a dependency changes).
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//
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// However, instead of forcing developers to declare a ko.computed property explicitly, it's
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// nice to offer a utility function that declares a computed getter directly.
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// Implements `ko.defineProperty`
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function defineComputedProperty(obj, propertyName, evaluatorOrOptions) {
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var ko = this,
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computedOptions = { owner: obj, deferEvaluation: true };
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if (typeof evaluatorOrOptions === 'function') {
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computedOptions.read = evaluatorOrOptions;
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} else {
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if ('value' in evaluatorOrOptions) {
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throw new Error('For ko.defineProperty, you must not specify a "value" for the property. You must provide a "get" function.');
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}
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if (typeof evaluatorOrOptions.get !== 'function') {
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throw new Error('For ko.defineProperty, the third parameter must be either an evaluator function, or an options object containing a function called "get".');
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}
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computedOptions.read = evaluatorOrOptions.get;
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computedOptions.write = evaluatorOrOptions.set;
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}
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obj[propertyName] = ko.computed(computedOptions);
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track.call(ko, obj, [propertyName]);
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return obj;
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}
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// Array handling
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// --------------
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//
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// Arrays are special, because unlike other property types, they have standard mutator functions
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// (`push`/`pop`/`splice`/etc.) and it's desirable to trigger a change notification whenever one of
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// those mutator functions is invoked.
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//
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// Traditionally, Knockout handles this by putting special versions of `push`/`pop`/etc. on observable
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// arrays that mutate the underlying array and then trigger a notification. That approach doesn't
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// work for Knockout-ES5 because properties now return the underlying arrays, so the mutator runs
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// in the context of the underlying array, not any particular observable:
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//
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// // Operates on the underlying array value
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// myModel.someCollection.push('New value');
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//
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// To solve this, Knockout-ES5 detects array values, and modifies them as follows:
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// 1. Associates a hidden subscribable with each array instance that it encounters
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// 2. Intercepts standard mutators (`push`/`pop`/etc.) and makes them trigger the subscribable
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// Then, for model properties whose values are arrays, the property's underlying observable
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// subscribes to the array subscribable, so it can trigger a change notification after mutation.
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// Given an observable that underlies a model property, watch for any array value that might
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// be assigned as the property value, and hook into its change events
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function notifyWhenPresentOrFutureArrayValuesMutate(ko, observable) {
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var watchingArraySubscription = null;
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ko.computed(function () {
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// Unsubscribe to any earlier array instance
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if (watchingArraySubscription) {
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watchingArraySubscription.dispose();
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watchingArraySubscription = null;
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}
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// Subscribe to the new array instance
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var newArrayInstance = observable();
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if (newArrayInstance instanceof Array) {
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watchingArraySubscription = startWatchingArrayInstance(ko, observable, newArrayInstance);
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}
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});
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}
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// Listens for array mutations, and when they happen, cause the observable to fire notifications.
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// This is used to make model properties of type array fire notifications when the array changes.
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// Returns a subscribable that can later be disposed.
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function startWatchingArrayInstance(ko, observable, arrayInstance) {
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var subscribable = getSubscribableForArray(ko, arrayInstance);
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return subscribable.subscribe(observable);
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}
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// Gets or creates a subscribable that fires after each array mutation
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function getSubscribableForArray(ko, arrayInstance) {
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var subscribable = arrayInstance[SUBSCRIBABLE_PROPERTY];
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if (!subscribable) {
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subscribable = new ko.subscribable();
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Object.defineProperty(arrayInstance, SUBSCRIBABLE_PROPERTY, {
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value : subscribable
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});
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var notificationPauseSignal = {};
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wrapStandardArrayMutators(arrayInstance, subscribable, notificationPauseSignal);
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addKnockoutArrayMutators(ko, arrayInstance, subscribable, notificationPauseSignal);
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}
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return subscribable;
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}
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// After each array mutation, fires a notification on the given subscribable
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function wrapStandardArrayMutators(arrayInstance, subscribable, notificationPauseSignal) {
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['pop', 'push', 'reverse', 'shift', 'sort', 'splice', 'unshift'].forEach(function(fnName) {
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var origMutator = arrayInstance[fnName];
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arrayInstance[fnName] = function() {
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var result = origMutator.apply(this, arguments);
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if (notificationPauseSignal.pause !== true) {
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subscribable.notifySubscribers(this);
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}
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return result;
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};
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});
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}
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// Adds Knockout's additional array mutation functions to the array
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function addKnockoutArrayMutators(ko, arrayInstance, subscribable, notificationPauseSignal) {
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['remove', 'removeAll', 'destroy', 'destroyAll', 'replace'].forEach(function(fnName) {
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// Make it a non-enumerable property for consistency with standard Array functions
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Object.defineProperty(arrayInstance, fnName, {
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enumerable: false,
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value: function() {
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var result;
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// These additional array mutators are built using the underlying push/pop/etc.
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// mutators, which are wrapped to trigger notifications. But we don't want to
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// trigger multiple notifications, so pause the push/pop/etc. wrappers and
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// delivery only one notification at the end of the process.
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notificationPauseSignal.pause = true;
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try {
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// Creates a temporary observableArray that can perform the operation.
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result = ko.observableArray.fn[fnName].apply(ko.observableArray(arrayInstance), arguments);
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}
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finally {
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notificationPauseSignal.pause = false;
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}
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subscribable.notifySubscribers(arrayInstance);
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return result;
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}
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});
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});
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}
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// Static utility functions
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// ------------------------
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//
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// Since Knockout-ES5 sets up properties that return values, not observables, you can't
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// trivially subscribe to the underlying observables (e.g., `someProperty.subscribe(...)`),
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// or tell them that object values have mutated, etc. To handle this, we set up some
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// extra utility functions that can return or work with the underlying observables.
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// Returns the underlying observable associated with a model property (or `null` if the
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// model or property doesn't exist, or isn't associated with an observable). This means
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// you can subscribe to the property, e.g.:
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//
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// ko.getObservable(model, 'propertyName')
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// .subscribe(function(newValue) { ... });
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function getObservable(obj, propertyName) {
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if (!obj /*|| typeof obj !== 'object'*/) {
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return null;
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}
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var allObservablesForObject = getAllObservablesForObject(obj, false);
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return (allObservablesForObject && allObservablesForObject[propertyName]) || null;
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}
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// Causes a property's associated observable to fire a change notification. Useful when
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// the property value is a complex object and you've modified a child property.
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function valueHasMutated(obj, propertyName) {
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var observable = getObservable(obj, propertyName);
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if (observable) {
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observable.valueHasMutated();
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}
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}
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// Extends a Knockout instance with Knockout-ES5 functionality
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function attachToKo(ko) {
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ko.track = track;
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ko.getObservable = getObservable;
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ko.valueHasMutated = valueHasMutated;
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ko.defineProperty = defineComputedProperty;
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}
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export default {
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attachToKo : attachToKo
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};
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