DHIS2 tracker capture custom form

form

<p>
<input id="ZzYYXq4fJie-GQY2lXrypjO-val" name="entryfield" title="GQY2lXrypjO - MCH Infant Weight  (g) - undefined" value="[MCH Infant Weight  (g)]" />

</p>

<p id="bmi-text">&nbsp;</p>
<script>
$(document).ready(function(){
function setColor(color){
$("p#bmi-text").css('background-color',color);
}

function updateBMI(){
var w=$("#ZzYYXq4fJie-GQY2lXrypjO-val").val();
var bmi=Math.pow(w,2);
$("p#bmi-text").text(bmi);
if(bmi<10){
setColor('red');
}else if(bmi<20){
setColor('yellow');
}else{
setColor('green');
}
}


$("#ZzYYXq4fJie-GQY2lXrypjO-val").on('keyup',function(){
updateBMI();
});

});




</script>