Change javascript VAR value with HTML select [closed]

Create a non-constant variable to store the value:

let difficulty; // you can give it a default value if you want

Then, use .addEventListener() to listen for changes and update your variable:

const difficultySelector = document.getElementById('nivel');
difficultySelector.addEventListener('change', () => {
    difficulty = difficultySelector.value;
});

You have a some syntax and logical error in your code.

1. const declaration mean that you can't change the value through your code once you set it.

2. you're trying to call variable lie a function using 'onChange' event

The solution:

3. declare your variable as a dynamic variable

4. create a function to reset its value

let BRICK_ROWS = 0;
function SET_BRICK_ROWS() {
BRICK_ROWS = document.getElementById('nivel').value; 
console.log(BRICK_ROWS)
}

 <select id='nivel'  onchange='SET_BRICK_ROWS()'>
        <option value="1">easy</option>
        <option value="2">medium</option>
        <option value="3">hard</option>
      </select>

Note: You can use addEventListener If you want a better solution

First: you can`t declare a const and then change this value. You should declare a var or let. Then to get select value:

<select id="nivel" onchange="changeValue(event)">
  <option value="1">easy</option>
  <option value="2">medium</option>
  <option value="3">hard</option>
</select>
<script>
  var brickRowsValue = 0
  function changeValue(event) {
    brickRowsValue = event.target.value
  }
</script>