If you backspace over the INPUT prompt "? " and enter text it hangs or throws a JS exception

[mobluse]

If you backspace over the INPUT prompt "? " and enter text it hangs or throws a JS exception. Run the test program below and press BACKSPACE once and then e.g. P and Enter; the browser tab hangs after a while. If you delete more before entering text, you get: "EXCEPTION RangeError: Invalid string length". I think it would be better if backing over the prompt was disallowed (as it is in your pcbasic) or it didn't hang or threw an exception, but instead sent the typed characters and ignored more backspaces than was needed. Now there is a great risk that a user hangs a program that they have worked with, to get a result, for a long time.

1000 A=100: GOTO 20: REM INPUT TEST
1010 INPUT "ENTER A STRING";A$
1020 PRINT "THE STRING IS: ";A$
1030 GOTO 1010
30000 REM DEMONSTRATES A BUG IN INPUT
30010 REM ENTER BACKSPACE AND A CHARACTER AND ENTER: IT HANGS.
30030 REM ENTER SEVERAL BACKSPACES AND A CHARACTER: A JS EXCEPTION.
30040 REM WHAT I EXPECTED: EITHER THAT BACKSPACE WOULDN'T BACK
30050 REM OVER THE PROMPT "? ", OR THAT IT WOULD ACCEPT THE TYPED
30060 REM CHARACTERS AS INPUT.

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