helper to debug when you don't know who or what is changing a value. Can log sets and gets, or even provide stacktraces to the offenders. Meant as a last resort debugging tool.

LibHelpers.js

var defaultMax = 1000;
function GetterSetterValue(initVal, logGet, logSet, traceSet, traceGet, max) {
	max = max === undefined ? defaultMax : max;
	this.originalMax = max;
	this._value = initVal;
	this.__logGet = logGet !== false;
	this.__logSet = logSet !== false;
	this.__traceGet = traceGet !== false;
	this.__traceSet = traceSet !== false;
	this.__countLogGet = max;
	this.__countLogSet = max;
	this.__countTraceGet = max;
	this.__countTraceSet = max;
}

GetterSetterValue.prototype = {
	_value: 0,
	__count: defaultMax,
	get value() {
		if(this.__logGet && this.__countLogGet >= 0) {
			console.log("getting", this._value);
			if(this.__countLogGet == 0) {
				console.log("max number of get logs reached (", this.originalMax, ")")
			}
			this.__countLogGet--;
		}
		if(this.__traceGet && this.__countTraceGet >= 0) {
			try {
				throw Error("Who read this value?");
			} catch(err) {
				console.log(err.message);
				console.log(err.stack);
			}
			if(this.__countTraceGet == 0) {
				console.log("max number of get traces reached (", this.originalMax, ")")
			}
			this.__countTraceGet--;
		}
		return this._value;
	},
	set value(val) {
		if(this.__logSet && this.__countLogSet >= 0) {
			console.log("setting", val);
			if(this.__countLogSet == 0) {
				console.log("max number of set logs reached (", this.originalMax, ")")
			}
			this.__countLogSet--;
		}
		if(this.__traceSet && this.__countTraceSet >= 0) {
			try {
				throw Error("Who wrote this value?");
			} catch(err) {
				console.log(err.message);
				console.log(err.stack);
			}
			if(this.__countTraceSet == 0) {
				console.log("max number of set traces reached (", this.originalMax, ")")
			}
			this.__countTraceSet--;
		}
		this._value = val;
	}
}

LibHelpers = {
	GetterSetterValue: GetterSetterValue
}

This is mostly meant to debug pesky in-place vars defined and manipulated in a function. It was born of a need to figure out what was wrong with geometry I was trying to parse with Three.js. It's a bit hacky because you do need to replace all instances of offendingVar with offendingVar.value, but in large libraries where its almost impossible to keep track of everything that manipulates a particular value, this can be a lifesaver.
For example:

function stuffDoer() {
    var offendingVar = 0;
    function cleverStuff(really) {
        if(really) offendingVar++;
    }
    cleverStuff(true);
    cleverStuff(false);
    cleverStuff(0);
    offendingVar = 0;
    cleverStuff(true);
}

To use this helper, include it in the html:

    <script type="text/javascript" src="../../lib/LibHelpers.js"></script>

and modify the suspicious code:

function stuffDoer() {
    var offendingVar = new LibHelpers.GetterSetterValue(0, true, true, true, true, 10);
    function cleverStuff(really) {
        if(really) offendingVar++;
    }
    cleverStuff(true);
    cleverStuff(false);
    cleverStuff(0);
    offendingVar = 0;
    cleverStuff(true);
}

And you should get a flood of logs pertaining to anything that reads or writes to offendingVar.value