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Forked from eligrey/object-watch.js
Last active November 8, 2019 06:40
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Fork of object.watch polyfill in ES5. Modified to not react when the value set is the same as previous.
/*
* object.watch polyfill
*
* 2012-04-03
*
* By Eli Grey, http://eligrey.com
* Public Domain.
*
* Modified by Nenad Damnjanović
* Nov 9, 2014
*
* NO WARRANTY EXPRESSED OR IMPLIED. USE AT YOUR OWN RISK.
*/
// object.watch
if (!Object.prototype.watch) {
Object.defineProperty(Object.prototype, "watch", {
enumerable: false
, configurable: true
, writable: false
, value: function (prop, handler) {
var
oldval = this[prop]
, getter = function () {
return oldval;
}
, setter = function (newval) {
if (oldval !== newval) {
handler.call(this, prop, oldval, newval);
oldval = newval;
}
else { return false }
}
;
if (delete this[prop]) { // can't watch constants
Object.defineProperty(this, prop, {
get: getter
, set: setter
, enumerable: true
, configurable: true
});
}
}
});
}
if (!Object.prototype.unwatch) {
Object.defineProperty(Object.prototype, "unwatch", {
enumerable: false
, configurable: true
, writable: false
, value: function (prop) {
var val = this[prop];
delete this[prop]; // remove accessors
this[prop] = val;
}
});
}
/**
*
* Example usage:
*
*
var o = {p: 1};
o.watch("p", function (id, oldval, newval) {
console.log( "o." + id + " changed from " + oldval + " to " + newval );
return newval;
});
o.p = 2; // should log the change
o.p = 2; // should do nothing
*
*
*/
@inoas
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inoas commented Jan 16, 2018

Thank you!

p.s.: I wonder if by standard it should trigger if a variable is set to the same value again.

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