If statement……Help

Please could someone help on how to add an if statement or any conditional statement to the below function such that if a (I am using a dynamic form) field is not displayed on the form, the function will skip to the next field available………..till the end function

here is the function

function passDate(str) {
document.device.PRE_idTESTDATE_.value = str;
for(i=0; i<document.device.PRE_idTESTDATE_.length; i++){
document.device.PRE_idTESTDATE_[i].value = str;
}
document.device.TUE_idTESTDATE_.value = str;
for(i=0; i<document.device.TUE_idTESTDATE_.length; i++){
document.device.TUE_idTESTDATE_[i].value = str;
}
}

function passTechnicianname(str1){
document.device.PRE_idTECHNICIANNAME_.value = str1;
for(i=0; i<document.device.PRE_idTECHNICIANNAME_.length; i++){
document.device.PRE_idTECHNICIANNAME_[i].value = str1;
}
document.device.TUE_idTECHNICIANNAME_.value = str1;
for(i=0; i<document.device.TUE_idTECHNICIANNAME_.length; i++){
document.device.TUE_idTECHNICIANNAME_[i].value = str1;
}
document.device.SUN_idTECHNICIANNAME_.value = str1;
for(i=0; i<document.device.SUN_idTECHNICIANNAME_.length; i++){
document.device.SUN_idTECHNICIANNAME_[i].value = str1;
}
document.device.MON_idTECHNICIANNAME_.value = str1;
for(i=0; i<document.device.MON_idTECHNICIANNAME_.length; i++){
document.device.MON_idTECHNICIANNAME_[i].value = str1;
}
}

function passMonthyear(str2) {
document.device.PRE_idMONTHYEAR_.value = str2;
for(i=0; i<document.device.PRE_idMONTHYEAR_.length; i++){
document.device.PRE_idMONTHYEAR_[i].value = str2;
}
document.device.TUE_idMONTHYEAR_.value = str2;
for(i=0; i<document.device.TUE_idTECHNICIANNAME_.length; i++){
document.device.TUE_idMONTHYEAR_[i].value = str2;
}
document.device.SUN_idMONTHYEAR_.value = str2;
for(i=0; i<document.device.SUN_idTECHNICIANNAME_.length; i++){
document.device.SUN_idMONTHYEAR_[i].value = str2;
}
document.device.MON_idMONTHYEAR_.value = str2;
for(i=0; i<document.device.MON_idTECHNICIANNAME_.length; i++){
document.device.MON_idMONTHYEAR_[i].value = str2;
}
}

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