如何避免做同样事情的if-else语句？

Question

I'm trying to minimize a little js program, and I came across this problem: I do not want to write a lot of if-else statements that they all do the same thing. Is there an elegant way to rewrite this function?

function advance_bthrads(toCompare, arr) {
    arr.forEach(function(element) {
        if (element.value) {
            let wf = element.value['wait_for'];
            let req = element.value['request'];
            if (wf && req) {
                if (toCompare === wf[0] || toCompare === req[0]) {
                    element = update_element(element);
                }
            } else if (wf) {
                if (toCompare === wf[0]) {
                    element = update_element(element);
                }
            } else if (req) {
                if (toCompare === req[0]) {
                    element = update_element(element);
                }
            }
        }
    });
    return arr;
}

Answer 1

forEach doesn't return anything - use map :

arr = arr.map(element => {
  if (element.value) {
    let [wf] = element.value['wait_for'] || [0];
    let [req] = element.value['request'] || [0];
    if (wf && req && [wf, req].includes(toCompare)) element = update_element(element);
  }
  return element;
});

Answer 2

Ignoring for a moment the fact that element = update_element(element); achieves nothing (as you're just updating the local element , not what it references) your condition can be reduced to simply

if((wf && wf[0] == toCompare) || (req && toCompare == req[0]))

Since the basic check is whether toCompare equals either wf[0] or req[0] and you basically add a check to see if wf and req exist.

At this point you can use map instead of forEach to get the result you want. Notice you have to return the map, and whatever function calls advance_bthreads needs to reassign the result (ie arr = advance_bthreads(toCompare, arr); )

function advance_bthrads(toCompare, arr) {
    return arr.map(function(element) { // NOTICE you have to return the result
        if (element.value) {
            let wf = element.value['wait_for'];
            let req = element.value['request'];
            if((wf && wf[0] == toCompare) || (req && toCompare == req[0]))
                element = update_element(element);
        }
        return element;
    }
}

Answer 3

You could short it a bit by returning early and combining the conditions.

BTW, the assignment does not work as intended, you need to use the element of the array with an index.

If update_element mutates element , then no assignment is necessary.

 function advance_bthrads(toCompare, arr) { arr.forEach(function(element, index, array) { if (!element.value) return; let wf = element.value['wait_for']; let req = element.value['request']; if (wf && toCompare === wf[0] || req && toCompare === req[0]) { array[index] = update_element(element); } }); return arr; }