returns first key that passes predicate

findKey.js

function findKey(obj, predicate) {
    for (var prop in obj) {
        if(obj.hasOwnProperty( prop ) ) {
            if (predicate(obj[prop])) {
                return prop;
            }
        } 
    }
}

function partial (fn) {
    var initialArgs = Array.prototype.slice.call(arguments, 1);
    return function () {
        var remainingArgs = Array.prototype.slice.call(arguments);
        return fn.apply({}, initialArgs.concat(remainingArgs));
    }
}

function compare(id, obj) {
    return id === obj.id;
}

//usage
objArr = {
    hello: {name: 'a', id:1},
    goodbye: {name: 'b', id:2},
    yahoo: {name: 'c', id:3}
};

console.log(findKey(objArr, partial(compare, 2)));