[Nexus]

var keyValuePairs = {
    '6': '112',
    '20': '51',
    '22': '78',
    '26': '34',
    '32': '22',
    '35': '358',
};

var result = Object.keys(keyValuePairs)
    .map(key => ({
        key,
        value: keyValuePairs[key]
    }))
    .sort((a, b) => b.value - a.value)
    .slice(0, 1)
    .reduce((res, item) => {
        res[item.key] = item.value;

        return res;
    }, {});

alert(JSON.stringify(result));