javascript remove (empty) array from assoc array

Question

I have an assoc js array and i want to remove one element from it. My solution works but it is not really nice, is there a better solution?

// i got this assoc array
var cm = [];
    cm["a"] = ["a"];
    cm["b"] = ["c"];
    cm["s"] = ["a", "b", "c"];
    cm["x"] = [];
console.log(cm);

var searchKey = "s";
var p = ["a","c","d", "b"]; // to remove from searchKey array

// remove elements (works fine)
cm[searchKey] = cm[searchKey].filter(value => (p.includes(value) === false));
console.log(cm); // now cm[searchKey] is an empty array

// if the array at index 'searchKey' is empty remove it from assoc array
var newarray = [];
if (cm[searchKey].length===0)
{
    for(key in cm)
  {
    if (key!=searchKey) newarray[key] = cm[key];
  }
}
cm = newarray;
console.log(cm);

I tried with filter and splice, but both works only at arrays not assoc array.

JavaScript doesn't have associative arrays. You're misusing the JS Array type. — user2437417
– user2437417, Commented Apr 24, 2018 at 16:59
cm is not an associative array. You shouldn't be doing that - you are actually making an array but then just treating it as an object by setting properties on it. You should be instantiating an object instead by using cm = {} — VLAZ
– VLAZ, Commented Apr 24, 2018 at 16:59
Seems that you want your code reviewed and improved, but you haven't given qualifications for what counts as "nice" or "better" code. — user2437417
– user2437417, Commented Apr 24, 2018 at 17:00
You're right, but the upper part (the 'assoc' array) is given (dont ask why) the hole array is handled like an object. delete works! — Sebastian
– Sebastian, Commented Apr 24, 2018 at 17:07
@Sebastian yes, delete would work. Just because you can do something doesn't mean you should. — VLAZ
– VLAZ, Commented Apr 24, 2018 at 17:13

dave · Accepted Answer · 2018-04-24 18:10:20Z

2

You have an object, so you can just do:

if (cm[searchKey].length===0)
{
    delete cm[searchKey]
}

edited Apr 24, 2018 at 18:10

answered Apr 24, 2018 at 16:59

dave

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Comments

motss · Accepted Answer · 2018-04-24 17:13:15Z

1

You might need Map. I think Map does a better job that you actually ask for.

answered Apr 24, 2018 at 17:13

motss

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Comments

Jonas Wilms · Accepted Answer · 2018-04-24 17:25:55Z

This is a perfect usecase for a Map:

  class Multimap extends Map {
    get(key) {
      return super.get(key) || [];
    }

    addTo(key, value) {
      if(this.has(key)) {
         this.get(key).push(value);
       } else {
         this.set(key, [value]);
       }
    }

    removeFrom(key, value) {
      this.set(key, this.get(key).filter(el => el !== value));
    }
}

This can be used as:

 const cm = new Multimap([
  ["a", ["a", "b", "c"]]
 ]);

 cm.removeFrom("a", "b");
 cm.get("a").includes("b") // false

Chris · Accepted Answer · 2020-03-20 13:01:51Z

0

I used .filter on the array like so

// Remove emptys
modeSummary = modeSummary.filter(ms => ms);

answered Mar 20, 2020 at 13:01

Chris

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