oxjs/source/Ox/js/Function.js

'use strict';

/*@
Ox.cache <f> Memoize a function
    <script>
        Ox.test.fn = Ox.cache(function(n) { return n * Math.random(); });
    </script>
    > Ox.test.fn(10) == Ox.test.fn(10);
    true
    > Ox.test.fn(10) == Ox.test.fn.clear()(10);
    false
@*/
// TODO: add async test
Ox.cache = function(fn, options) {
    var cache = {},
        ret = function() {
            options = Ox.extend({
                async: false,
                key: JSON.stringify
            }, options || {});
            var args = Ox.toArray(arguments), key = options.key(args);
            function callback() {
                // cache all arguments passed to callback
                cache[key] = Ox.toArray(arguments);
                // call the original callback
                Ox.last(args).apply(this, arguments);
            }
            if (options.async) {
                if (!(key in cache)) {
                    // call function with patched callback
                    fn.apply(this, args.slice(0, -1).concat(callback));
                } else {
                    // call callback with cached arguments
                    callback.apply(this, cache[key])
                }
            } else {
                if (!(key in cache)) {
                    cache[key] = fn.apply(this, args);
                }
                return cache[key];
            }
        };
    ret.clear = function() {
        if (arguments.length == 0) {
            cache = {};
        } else {
            Ox.makeArray(arguments).forEach(function(key) {
                delete cache[key];
            });
        }
        return ret;
    };
    return ret;
};

/*@
Ox.identity <f> Returns its first argument
    This can be used as a default iterator
    > Ox.identity(Infinity)
    Infinity
@*/
Ox.identity = function(value) {
    return value;
};

/*@
Ox.noop <f> Returns undefined and calls optional callback without arguments
    This can be used as a default iterator in an asynchronous loop, or to
    combine a synchronous and an asynchronous code path.
    > Ox.noop(1, 2, 3)
    undefined
    > Ox.noop(1, 2, 3, function() { Ox.test(arguments.length, 0); })
    undefined
@*/
Ox.noop = function() {
    var callback = Ox.last(arguments);
    Ox.isFunction(callback) && callback();
};