debounced promise

promiseDebounce.js

/*
Debounce promises.

Prevents multiple calls if the request is the same and either:
1. the promise has not resolved yet
2. a delay of {timeout} milliseconds has not passed since the last call

The call identity is dependent upon a key created with JSON.stringify(arguments)
*/
var debouncePromise = function debouncePromise(methodName, promise, throttleTimeout) {
	var timeout = {};
	var pendingPromise = {};
	var isPromiseDone = {};
	var isTimeoutDone = {};
	var clearDebounceVariables = function clearDebounceVariables(cacheKey) {
	    delete isTimeoutDone[cacheKey];
	    delete isPromiseDone[cacheKey];
	    delete pendingPromise[cacheKey];
	    delete timeout[cacheKey];
	};
	var setCustomTimeout = function setCustomTimeout(cacheKey) {
	    clearTimeout(timeout[cacheKey]);
	    timeout[cacheKey] = setTimeout(function () {
	        isTimeoutDone[cacheKey] = true;
	        if (isPromiseDone[cacheKey]) {
	            clearDebounceVariables(cacheKey);
	        }
	    }, throttleTimeout);
	};
	
	return function debouncedPromise() {
	    var cacheKey = JSON.stringify(arguments);
	
	    if (pendingPromise[cacheKey]) {
	        setCustomTimeout(cacheKey);
	
	        console.log('Debouncing ' + methodName + ' that was called with ' + cacheKey);
	        return pendingPromise[cacheKey];
	    }
	
	    isPromiseDone[cacheKey] = false;
	
	    if (!throttleTimeout[cacheKey]) {
	        isTimeoutDone[cacheKey] = true;
	    } else {
	        setCustomTimeout(cacheKey);
	    }
	
	    pendingPromise[cacheKey] = promise.apply(null, arguments)
	        .then(function (result) {
	            isPromiseDone[cacheKey] = true;
	            if (isTimeoutDone[cacheKey]) {
	                clearDebounceVariables(cacheKey);
	            }
	
	            return result;
	        })
	        .catch(function (result) {
	            isPromiseDone[cacheKey] = true;
	            if (isTimeoutDone[cacheKey]) {
	                clearDebounceVariables(cacheKey);
	            }
	
	            return result;
	        });
	
	    return pendingPromise[cacheKey];
	};
};