fp via js

// const IF = a => f => a && f(a);
var IF = (b, a) => f => b && f(a || b);
// var If = (b, a) => f1 => f0 => (b ? f1 : f0)(a);
const If = (a, fb) => f1 => f0 => (b => b ? f1(b) : f0(a))(fb(a));

// 1:
let id = defaultId || If([].slice.call(eventRow.children[1].querySelectorAll('a'), 0, -1), a => a.reverse()[1])(a => a.href)(ar => ar[0].href);

// 2:
let id;
if (defaultId) id = defaultId
else{
    let arr = [].slice.call(eventRow.children[1].querySelectorAll('a'), 0, -1);

    let a = arr.reverse()[1]
    id = a ? a.href : arr[0] .href;
}