client_script.js

frappe.call({
    "method":"frappe.client.get_list",
    "args":{
        "doctype":"Purchase Invoice",
        "filters": { "docstatus": 1}
    },
    callback: function(r){
        if(r && r.message && r.message.length > 0){
            for(var i=0; i< r.message.length; i++){
                console.log(r.message[i].name) //It will be the name of purchase invoice
            }
        }
    }
});