how to set value in jquery code example

Example 1: jquery change value

$('#opacity').val(100);
$('#opacity').val("hello");

Example 2: jquery set input value

$("button").click(function(){
  $("input:text").val("Glenn Quagmire");
 })

Example 3: assign input text value jquery

<?= $this->Form->input('number_six', array(
     'label' => false,
     'class' => 'form-control number_six',
     'maxlength' => "1" ,
     'oninput' => "this.value=this.value.replace(/[^0-9]/g,'');"
   ));?>

$(".number_six").val("");