check to see if vendor is inactive

Im still learning suitescripting so bare with me :h_a_w:

So when a PO is being copied and the vendor is inactive i would like to show an alert on screen to inform user. Below is what i have thus far and im getting a runtime error message whenever i go into a PO now.

function sb_onPageInit(type) {
var vend = nlapiGetFieldValue('vendor.inactive')
   if(type == 'copy' && vent = 'true'){
   alert("The PO you are copying has an inactive vendor");
} else {


        try {
            nlapiSetFieldValue('custbody_approverassigned','');
            nlapiSetFieldValue('custbody_accounting','F');

            nlapiSetFieldValue('custbody_alt_approval','');
            nlapiSetFieldValue('custbody_alternate1_approved','F');