Whats the purpose of these lines in the script?

Frappe Framework Custom Script
1

Hullo members,

thanks for the great support, am using this script to compute and its working well but can some one explain to me the purpose of the last 2 lines in the script. I need this for learning purposes, the lines are cur_frm.cscript.custom_invoice_amount = compute; & cur_frm.cscript.custom_total_amount_paid = compute; as shown in script below, thanks in advance.

function compute(doc, cdt, cdn){
if (doc.invoice_amount && doc.total_amount_paid){ //it checks if the fields contains a value
doc.pending_payment = doc.invoice_amount + doc.total_amount_paid * 10;
refresh_field(“pending_payment”);
}
else {
doc.pending_payment = doc.invoice_amount;
refresh_field(“pending_payment”);
}
}

cur_frm.cscript.custom_invoice_amount = compute;
cur_frm.cscript.custom_total_amount_paid = compute;

2

Your custom function is assigned to the custom script for execution.

3

Thanks for the reply, am new to programming but would like to understand, why do we add custom_ to the field name, and we add = compute. I feel understanding this script will move me a major step further in programming.

thanks in advance.