Setting value for UOM in Purchase Order

ERPNext
1

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?

2

you have to apply the client script for that.

like

if (row.billing_type == "Type 1") {
    row.uom = "Nos"
}
3

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

4

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