which checkbox is checked javascript code example

Example 1: fill checkbox javascript

// Check
document.getElementById("checkbox").checked = true;

// Uncheck
document.getElementById("checkbox").checked = false;

Example 2: oncheck checkbox javascript

<input type='checkbox' onchange='handleChange(this);'> Checkbox

function handleChange(checkbox) {
    if(checkbox.checked == true){
        document.getElementById("submit").removeAttribute("disabled");
    }else{
        document.getElementById("submit").setAttribute("disabled", "disabled");
   }
}