Simplifying a nested loop in a javascript function-CodePudding

I have this function in JS

function getMap(objectList) {
  const objectMap = new Map();
  IDS.foreach(id => {
    const attribute = objectList.find(object => object.getId() === id);
    if (attribute) {
      objectMap.set(id, attribute);
    } else {
      objectMap.set(id, null);
    }
}

This is a nested loop because of the find inside the for loop. How could this be simplified? If the nested loop cannot be simplified, can other parts be simplified?

CodePudding user response：

Assuming object IDs are unique, it looks like all you really have to do is call getId on each object beforehand. The conditional operator may be used instead of if/else if you wish.

function getMap(objectList) {
    const objectsById = new Map(
        objectList.map(object => [object.getId(), object])
    );
    const objectMap = new Map();
    for (const id of IDS) {
        objectMap.set(id, objectsById.get(id) || null);
    }
}

CodePudding user response：

You could create an array with null entries for each ID, followed by entries for which you actually have values in objectList, and pass that array to the Map constructor:

function getMap(objectList) {
  return new Map([
    ...IDs.map(id => [id, null]),
    ...objectList.map(object => [object.getId(), object])
  ]);
}

CodePudding user response：

Using native code with a simple callback

const result = (IDS || []).map(function(id, idx, arr) {
    const pos = (objectList || []).findIndex(object => object.getId() === id);
    const output = [];
    output[id] = (pos >= 0 ? objectList[pos] : null);
    return output;
});

Hope this helps... ;D