Question
How to I do to let the specific field be hidden?
1) Initially, Field A and Field B are visible for person to input.

2) During input some words in Field A (eg. Peter)

3) After input words, Field B is hidden. Person cannot input anything in Field B.

4) If I delete the words in field A (Become blank), Field B becomes visible again.

I don't know how to make the java-script code for this activity. Would you mind help me design? Thank You.
