function ClearForm(form){
    form.weight.value = "";
    form.height.value = "";
    form.bmi.value = "";
    }
function bmi(weight, height) {
          bmindx=weight/eval(height*height);
          return bmindx;
}
function checkform(form) {
       if (form.weight.value==null||form.weight.value.length==0 || form.height.value==null||form.height.value.length==0){
            alert("\nPlease complete the form first");
            return false;
       }
       else if (parseFloat(form.height.value) <= 0||
                parseFloat(form.height.value) >=500||
                parseFloat(form.weight.value) <= 0||
                parseFloat(form.weight.value) >=500){
                alert("\nI think you made an error. \nPlease enter values again. \nWeight in kilos and \nheight in centimetres");
                ClearForm(form);
                return false;
       }
       return true;
}
function computeform(form) {
       if (checkform(form)) {
       form.weight.value = form.weight.value ;
       form.height.value = form.height.value;
       yourbmi=Math.round(bmi(form.weight.value, form.height.value/100));
       form.bmi.value=yourbmi;
       form.weight.value = form.weight.value;
       form.height.value = form.height.value;
       }
       return;
}