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));