Question 321982 in Javascript Question posted in
A very good W3school tutorial can be found here.

Javascript – list of map nested in a set

I’m fairly new and trying to understand maps in javascript.

I have below code.

const topmap = new Map();

const map1 = new Map();
const map2 = new Map();

const set1 = new Set();

map1.set('x','y');
map1.set('a','b');

set1.add(map1);
set1.add(map2);
topmap.set('ID',set1);


console.log(topmap.get('ID').size);
topmap.get('ID').forEach(x => {
  if(x.has('x')){x.delete('x')} )
  
  }
)
console.log(topmap.get('ID').size)

Anyone has any idea why both lines getting their size returning 2 even tho i deleted one map in line 18

Tags:

2

Answers


  1. 0

    Because your topmap.get('ID').size represents your set1 has two map.
    You just delete map’s element rather than map.

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  2. 0

    On your code above at line if(x.has(‘x’)){x.delete(‘x’)} ), you redundant ) in end of line.

    If you want to remove the entire Map (map1) from the Set (set1), you can use the set1.delete(map1) method. Here’s the corrected code:

    const topmap = new Map();

const map1 = new Map();
const map2 = new Map();

const set1 = new Set();

map1.set('x', 'y');
map1.set('a', 'b');

set1.add(map1);
set1.add(map2);
topmap.set('ID', set1);

console.log(topmap.get('ID').size);

// Delete the Map from the Set
topmap.get('ID').forEach(x => {
  if (x.has('x')) {
    set1.delete(x);
  }
});

console.log(topmap.get('ID').size);  // Should log 1
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