Lucky ticket

Write a function isLuckyTicket(ticket) that checks if a bus ticket number is lucky.

• ticket is a string.
• The ticket is lucky when it has exactly 6 characters, every character is a digit from 0 to 9, and the sum of the first three digits equals the sum of the last three digits. '123321' is lucky: 1 + 2 + 3 = 6 and 3 + 2 + 1 = 6.
• Return a boolean: true for a lucky ticket, false otherwise.
• Any string that is not exactly 6 digits gives false: a shorter or longer string, the empty string, a string with letters or spaces.

Careful with +: '1' + '2' is '12', not 3. With a string, + means concatenation, and type coercion turns 0 + '1' into '01'. Turn every digit into a number before you add it.