happy_lights/main.js

let elem = document.getElementById('qq');

let a_click = false


function createTable (parent, cols, rows){  
let table = document.createElement('table')
document.onmousedown = function(){
    a_click = true
}

document.onmouseup = function(){
    a_click = false
}
let palitra = document.getElementById('palitra');

    for ( i=0; i<rows; i++){
      let tr=document.createElement('tr')  
       

        for (j=0; j<cols; j++){

           let td =  document.createElement('td')
           td.onmouseover = function(){
                if (a_click){

                    td.style.backgroundColor = palitra.value
                }


            }
            td.onclick = function(){
                td.style.backgroundColor = palitra.value
            }
               
           tr.append(td)
        }
        table.append(tr)
    }
    parent.append(table)
}

createTable (elem, 20, 20)