How to increase all values of a map in javascript

Question

I have this map:

var map = new Map();

map.set("10/10", 0);
map.set("10/11", 1);
map.set("10/12", 2);

     
{
   "10/10": 0,
   "10/11": 1,
   "10/12": 2,
}

And I want to add this new key/value:

"10/9": 0,

How can I increase the values of all the old map elements in 1? So I get the following map:

{
   "10/9": 0,
   "10/10": 1,
   "10/11": 2,
   "10/12": 3,
}

I am storing indices of a list in this map, for getting a fast indexing. — Conchi Bermejo
– Conchi Bermejo, Commented Jan 21, 2021 at 5:36
Iterate over the keys of the map and set them one by one?... — user202729
– user202729, Commented Jan 21, 2021 at 5:42
You do realize your example is flawed, right? The Map maintains insertion order - so "10/9' will be the last key in the list, it cannot be the first in your given scenario. — Randy Casburn
– Randy Casburn, Commented Jan 21, 2021 at 5:45
[...map.keys()].forEach(k => map.set(k, map.get(k) +1)); and then map.set("10/9", 0); — D. Seah
– D. Seah, Commented Jan 21, 2021 at 5:45

Taghi Khavari · Accepted Answer · 2021-01-21 05:49:41Z

2

You can use something like this:

var map = new Map();

map.set("10/10", 0);
map.set("10/11", 1);
map.set("10/12", 2);

function addNewItem(item, map) {
  map.forEach((value, key, map) => {
    map.set(key, value + 1);
  });
  map.set(item, 0);
  return map;
}

const newMap = addNewItem("10/9", map);

console.log(newMap);

answered Jan 21, 2021 at 5:49

Taghi Khavari

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Comments

sourav satyam · Accepted Answer · 2021-01-21 05:56:48Z

1

You can place the item at any position here based on its value and increment the value greater then or equal to assigned value.

var map = new Map();

map.set("10/10", 0);
map.set("10/11", 1);
map.set("10/12", 2);



function logMapElements(value, key, map, set_key, set_value) {
    if (set_value <= value) {
      map.set(key, value+1);
    }
    
}

function setMapElement(set_key, set_value) {
        map.forEach((key, value, map) => logMapElements(key, value, map, set_key, set_value))
    map.set(set_key, set_value);
  

  
  
}

setMapElement("10/9", 0);
console.log(map.get("10/9"));
console.log(map.get("10/10"));

answered Jan 21, 2021 at 5:56

sourav satyam

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