Purpose: To check if a SAP screen element exists and is visible or not. Both the options return true or false.
isValid - Can be used to check if a SAP screen element exists or not, i.e., if the control is sent from SAP even though it is not visible on the screen.
Syntax:if(<"F[GR/GI Slip No.]">.isValid)
// Check if the field exists set("V[z_migo_grgislipnum]","X");
isVisible - Can be used to check if a SAP screen element is visible or not on SAPgui.
Syntax:if(<"F[GR/GI Slip No.]">.isVisible)
// Check if the field is appears on SAPgui set("F[GR/GI Slip No.]", " ");
// Set it to blankExample-SAP R/3 - ZEUS [Internal to Synactive]
Inputfield - "GR/GI Slip No."
Transactions MIGO and Z_MIGO for Goods Issue. This field is valid on both the transactions, however only visible in MIGO and not Z_MIGO.
NOTE - Below is the link of another forum article where it is used:
http://www.guixt.com/forum/index.php?topic=81.msg85#msg85