javascript - How to prevent form submit JQuery -

i wish check if checkbox not checked, prevent form being submited. example, have 7 checkboxs(days) in form , if user click submit button without check 1 of checkboxs, display error message , prevent form being submited. if user check 1 of check box, run if-else below , if ok reduce slot 1. idea how it?

jquery code

var slot = 7;  $(".day").each(function(){     if($(this).is(":checked")){           var num = $('.day').index(this);          if($("[name='sd_input_dosage_value[]']").eq(num).val() == ""){             alert("the dosage required , cannot empty.");             return false;         }         else if(!$.isnumeric($("[name='sd_input_dosage_value[]']").eq(num).val())){             alert("the dosage not number.");             return false;         }         else if(parsefloat($("[name='sd_input_dosage_value[]']").eq(num).val()) < 0){             alert("the dosage cannot negative value.");             return false;         }         else if($("[name='sd_dosage_select_value[]']").eq(num).val() == ""){             alert("the dosage unit cannot empty.");             return false;                            }         else if($("[name='sd_input_quantity_value[]']").val() == ""){             alert("the quantity required , cannot empty.");             return false;         }         else if(!$.isnumeric($("[name='sd_input_quantity_value[]']").val())){             alert("the quantity not number.");             return false;         }         else if(parsefloat($("[name='sd_input_quantity_value[]']").val()) < 0){             alert("the quantity cannot negative value.");             return false;         }         else{             slot = slot -1;         }      }                    });  if(slot == 7){     alert("there must least 1 check box checked."); } 

you can use event.preventdefault() prevent form submitting;

based on assumptions of html structure:

// when form submitted $('form').on('submit', function(e) {      // number of checked checkboxes     if ($('input[name="days[]"]:checked').length) {         // code here     } else {         // prevent form submitting         e.preventdefault();     } });