Once

function once(fn, context) { 
    var result;

    return function() { 
        if(fn) {
            result = fn.apply(context || this, arguments);
            fn = null;
        }

        return result;
    };
}

//example
var canOnlyFireOnce = once(function() {
    console.log('yes!');
});

canOnlyFireOnce(); // "yes!"
canOnlyFireOnce(); // no