Push Changes to a document from another document

//Replace "DocType" with the source DocType
frappe.ui.form.on("DocType", {
 //The trigger can be changed, but refresh must be used to use a button
 refresh: function(frm) {
  //The following line creates a button.
  frm.add_custom_button(__("Update"),
   //The function below is triggered when the button is pressed.
   function() {
    frappe.call({
     "method": "frappe.client.set_value",
     "args": {
      //replace "Target DocType" with the actual target doctype
      "doctype": "Target DocType",
      //replace target_doctype_link with a link to the document to be changed
      "name": frm.doc.target_doctype_link,
      "fieldname": {
       //You can update as many fields as you want.  
       "target_field_1": frm.doc.source_field_1,
       "target_field_2": frm.doc.source_field_2,
       "target_field_3": frm.doc.source_field_3,
       "target_field_4": frm.doc.source_field_4,
       "target_field_5": frm.doc.source_field_5  //Make sure that you do not put a comma over the last value
      },
     }
    });
  });
 }
});