form.onsubmit = e => {
    if  (numberForm.value.length === 11) {
          e.preventDefault();
    }
};

const arrayTaskOne = ['a','b','c','d'];
function functionTaskOne (array) 
    let newArray = array;
    newArray.splice(0, 4, 'e', 'f', 'g', 'h');
    return newArray;
}
console.log(functionTaskOne(arrayTaskOne));