JS Function Utils: debounce, throttle, curry, memorize

js-function-utils

window.FunctionHelpers = {
    debounce: function(fn, threshold, execASAP) {
        var timeout = null;
        threshold = threshold || 100;
        return function() {
            var self = this;
            var args = arguments;
            var delayed = function() {
                if (!execASAP) {
                    fn.apply(self, args);
                }
                timeout = null;
            };
            if (timeout) {
                clearTimeout(timeout);
            } else if (execASAP) {
                fn.apply(self, args);
            }
            timeout = setTimeout(delayed, threshold);
        };
    },
    throttle: function(fn, threshold, alt) {
        var last = new Date(1970);
        threshold = threshold || 100;
        return function() {
            var now = Date.now();
            if (now - last < threshold) {
                if (alt) {
                    alt.apply(this, arguments);
                }
                return;
            }
            last = now;
            fn.apply(this, arguments);
        };
    },
    remember: function(fn, keyfn) {
        var results = {};
        return function() {
            var key = keyfn.apply(undefined, arguments);
            if (!results[key]) {
                results[key] = fn.apply(undefined, arguments);
            }
            return results[key];
        }
    },
    curry: function(fn) {
        var args = [].slice.call(arguments, 1),
            placeholder = arguments.callee.placeholder,
            placeholders = [];
        for (var i = 0; i < args.length; i++) {
            if (args[i] === placeholder) {
                placeholders.push(i);
            }
        }
        if (placeholders.length > 0) {
            return function() {
                var inputs = [].slice.call(arguments),
                    origin = args.slice();
                for (var i = 0; i < placeholders.length; i++) {
                    origin[placeholders[i]] = inputs.shift();
                }
                fn.apply(undefined, [].concat.apply(origin, inputs));
            };
        } else {
            return function() {
                fn.apply(undefined, [].concat.apply(args, arguments));
            };
        }
    }
}
window.FunctionHelpers.curry.placeholder = {};

Examples:
var logA = FunctionHelpers.debounce(function () {
	console.log('A');
}, 1000);
logA();
var logB = FunctionHelpers.throttle(function () {
	console.log('B');
}, 1000);
logB();
var logC = FunctionHelpers.curry(function () {
	console.log([].join.apply(arguments));
}, 'a', 'b');
logC('c');
var logC2 = FunctionHelpers.curry(function () {
	console.log([].join.apply(arguments));
}, window.FunctionHelpers.curry.placeholder, 'b2', 'c2');
logC2('a2');
var Fib = FunctionHelpers.remember(function (n) {
	console.log(n);
	switch (n) {
		case 1:
			return 1;
		case 2:
			return 2;
		default:
			return Fib(n-1) + Fib(n-2);
	}
}, function (n) {
	return n;
});
console.log(Fib(10));