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index.js
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index.js
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let objectMap = new Map();
function WatchO(object, optionalDefaultListener, optionalListOfFieldsToListen) {
// optionalDefaultListener will be added as the first listener - TO.DO
if (isWatchable(object)) {
//if optionalDefaultListener, optionalListOfFieldsToListen are given,
// attach them on the watchable TO.DO
return object;
}
if (objectMap.has(object)) {
let watchO = objectMap.get(object);
watchO._reshape(object);
// Object.assign(watchO,object);
return watchO
}
if (object && typeof object != "object")
throw new TypeError(
"Expected an object as first parameter, got "
+ (typeof object))
let reactiveObj;
let baseObject = {};
let closureFields;
let blockDespatch = false;
let hasPendingDespatch = false;
let listeners = new Set(); // parents
let lastKnownKeys = new Set(); // properties
let watchableChildren = new Map();
let isActive = true;
let pendingDespatch = null;
let nudgeWatcher = function nudgeWatcher(flag) {
if (flag == 'ifpending' && pendingDespatch === null) return;
//If already pending, return
if (pendingDespatch !== null) {
return;
}
pendingDespatch = setTimeout(() => {
adaptStructChanges(reactiveObj, reactiveObj, closureFields);
let summary = []; // list of keys changed TO.DO
listeners.forEach(listener => listener(summary))
pendingDespatch = null;
}, 0)
}
let onNotify = function onNotify(summary) {
// do something when a nudge is received from a child watchable
nudgeWatcher();
}
let destroy = function destroy() {
watchableChildren.forEach((watchable, key) => {
watchable._detachListener(onNotify);
})
isActive = false;
}
let activateIfDead = function activateIfDead() {
if (isActive || listeners.size == 0) return;
watchableChildren.forEach((watchable, key) => {
watchable._attachListener(onNotify)
})
isActive = true;
}
watchableChildren.$remove = (key) => {
watchableChildren.get(key)._detachListener(onNotify)
watchableChildren.delete(key);
}
watchableChildren.$add = (key, value) => {
value._attachListener(onNotify)
watchableChildren.set(key, value);
}
closureFields = {
object: baseObject,
set blockDespatch(val) { blockDespatch = val },
get blockDespatch() { return blockDespatch; },
// set isActive(val) { isActive = val; },
get isActive() { return isActive; },
get hasPendingDespatch() { return hasPendingDespatch; },
listeners,
lastKnownKeys,
watchableChildren,
nudgeWatcher,
onNotify,
activateIfDead,
destroy,
}
reactiveObj = generateReactiveStub(closureFields);
objectMap.set(object, reactiveObj);
adaptStructChanges(object, reactiveObj, closureFields);
return reactiveObj;
}
function adaptStructChanges(currentState, reactiveObj, closureFields) {
let { lastKnownKeys, watchableChildren, object: baseObject } = closureFields;
let currentKeys = new Set(Object.getOwnPropertyNames(currentState));
for (let key in currentState) {
currentKeys.add(key);
}
// first detatch removed items
lastKnownKeys.forEach(key => {
if (currentKeys.has(key)) { // if both set have them, its not a interesting key.
currentKeys.delete(key);
// if a watchable exists in the object-tree but not in watchableChildren, add it.
if (isWatchable(baseObject[key]) && !watchableChildren.has(key)) {
watchableChildren.$add(key, baseObject[key]);
}
} else {
delete reactiveObj[key];
lastKnownKeys.delete(key);
if (watchableChildren.has(key)) {
watchableChildren.$remove(key)
}
}
let propDesc = Object.getOwnPropertyDescriptor(reactiveObj, key);
if (propDesc && !propDesc.configurable)
throw new TypeError(`Could not modify PropertyDescriptor in currect state at object.${key}`)
})
// attach new properties. everything left in currentKeys is new
currentKeys.forEach(key => {
let propDescriptor = Object.getOwnPropertyDescriptor(currentState, key)
animateField(reactiveObj, key, propDescriptor, closureFields)
lastKnownKeys.add(key);
})
}
function animateField(reactiveObj, fieldName, propDescriptor, closureFields) {
propDescriptor.configurable = true;
let value = propDescriptor.value;
// if (Object.hasOwnProperty(reactiveObj, fieldName)) delete reactiveObj[fieldName];
if (isFunction(value)) {
propDescriptor.value = value = setApplyTrap(value, reactiveObj, closureFields)
}
else if (typeof value == "object") {
propDescriptor.value = value = WatchO(value); // Watchable will return same object if the baseobject is already a watchable
closureFields.watchableChildren.$add(fieldName, value);
}
Object.defineProperty(closureFields.object, fieldName, propDescriptor);
let watchoPropDescriptor = {
enumerable: true,
configurable: true
}
watchoPropDescriptor.set = (val) => {
closureFields.activateIfDead();
if (!propDescriptor.writable && !propDescriptor.get && !propDescriptor.set) return;
let oldVal = closureFields.object[fieldName];
let newVal = val;
if (isFunction(val)) {
if (val == oldVal || val == oldVal.prototype) return;
newVal = setApplyTrap(val, reactiveObj, closureFields)
}
else if (typeof val == "object") {
newVal = WatchO(val); // Watchable will return same object if the baseobject is already a watchable
if (oldVal == newVal) return;
closureFields.watchableChildren.$add (fieldName, newVal);
}
if (isWatchable(oldVal)) {
closureFields.watchableChildren.$remove(fieldName, oldVal);
}
if (newVal === oldVal) return;
closureFields.object[fieldName] = newVal;
closureFields.nudgeWatcher();
}
watchoPropDescriptor.get = () => {
closureFields.activateIfDead();
return closureFields.object[fieldName];
}
Object.defineProperty(reactiveObj, fieldName, watchoPropDescriptor)
}
function setApplyTrap(fn, context, closureFields) {
// equivalent of `apply` trap
let boundFn = fn.bind(context);
let wrappedFn = (...args) => {
let result = boundFn(...args);
closureFields.nudgeWatcher("ifpending");
return result;
}
Object.defineProperty(wrappedFn, "prototype", { configurable: false, enumerable: false, value: fn })
return wrappedFn
}
function isWatchable(object) {
return object instanceof WatchO;
}
// https://stackoverflow.com/a/7356528/2605574
function isFunction(functionToCheck) {
var getType = {};
return functionToCheck && getType.toString.call(functionToCheck) === '[object Function]';
}
function generateReactiveStub(closureFields) {
closureFields.blockDespatch = false;
let inheritedProto = Object.create(WatchO.prototype);
Object.defineProperty(inheritedProto, '_attachListener', {
value: function _attachListener(listener, optionalListOfFieldsToListen) {
// `optionalListOfFieldsToListen` if given, call listener only if a field in list is updated. TO.DO
if (isFunction(listener)) {
closureFields.listeners.add(listener);
// return closureFields.object;
}
}
})
Object.defineProperty(inheritedProto, '_detachListener', {
value: function _detachListener(listener) {
if (isFunction(listener))
closureFields.listeners.delete(listener);
if (closureFields.listeners.size == 0)
closureFields.destroy();
}
})
Object.defineProperty(inheritedProto, '_nudge', {
value: function _nudge() {
closureFields.nudgeWatcher();
}
})
Object.defineProperty(inheritedProto, '_reshape', {
value: function _reshape(object) {
closureFields.destroy();
closureFields.watchableChildren.clear();
closureFields.lastKnownKeys.clear();
Object.getOwnPropertyNames(reactiveObj).forEach(key => delete reactiveObj[key])
adaptStructChanges(object, reactiveObj, closureFields);
if (objectMap.get(object) != reactiveObj)
throw "Warning!! calling _reshape with any object other than the base object is discouraged. However, calling _reshape wrapped in a try-catch will yield the desired result."
}
})
let reactiveObj = Object.create(inheritedProto);
return reactiveObj;
}
try {
window.Rectangle.WatchO = WatchO
} catch (e) { module.exports = WatchO }