Setting value for UOM in Purchase Order

In Purchase Order Item have a custom field billing type. When selecting an option for billing type that option will be set as value for UOM.How?

you have to apply the client script for that.


if (row.billing_type == "Type 1") {
    row.uom = "Nos"

not getting updated uom value with below script.
function checkBillingType(item, frm) {
if (item.custom_billing_type !== ‘None’) {
item.uom = item.custom_billing_type

Check the child table syntax and set it according to the scenario.