var info = [{
desc: 'elem',
number: 10,
}, {
desc: 'elem2',
number: 20,
}, {
sum: 200,
}];
var sum = info.filter(i => i.sum).shift().sum;
var res = info.filter(i => i.number).map(m => (m.number / sum) * 100);
console.log(res);// [5, 10]