Tengo un problema para obtener valores de los campos de casilla de verificación, probé este método pero solo funciona en campos de tipo radio.
function writee(){ var x = document.forms["formz"].music.value oo=window.open(" ","tab","width=300,height=350") oo.document.open() oo.document.write(x) } <form name="formz"> What music do you prefer: <input type="checkbox" name="music" value="rock" > Rock <input type="checkbox" name="music" value="techno"> Techno <input type="checkbox" name="music" value="pop"> Pop </form> <button onclick="writee()">button</button> function writee(){ var markedCheckbox =document.querySelectorAll('input[type="checkbox"]:checked'); let checkedValues = ''; for (var checkbox of markedCheckbox) { checkedValues += checkbox.value + ' '; } console.log(checkedValues); // oo=window.open(" ","tab","width=300,height=350") // oo.document.open() // oo.document.write(x) } <form name="formz"> What music do you prefer: <input type="checkbox" value="rock" > Rock <input type="checkbox" value="techno"> Techno <input type="checkbox" value="pop"> Pop </form> <button onclick="writee()">button</button> function writee() { var checkboxes = Array.from(document.forms["formz"].music); var checked = checkboxes.filter((item) => item.checked); const values = checked.map((item) => item.value); console.log(values); } <form name="formz"> What music do you prefer: <input type="checkbox" name="music" value="rock" /> Rock <input type="checkbox" name="music" value="techno" /> Techno <input type="checkbox" name="music" value="pop" /> Pop </form> <button onclick="writee()">button</button>Lo acabo de modificar un poco.
Array.from() para que podamos usar métodos de matrizespero que esto responda la pregunta