Is the Sum of Letters Even or Odd?

Create a function that takes a string and returns true if the sum of the position of every letter in the alphabet is even and false if the sum is odd.

Examples

isAlpha("i'am king")  ➞ true
// 9 + 1 + 13 + 11 + 9 + 14 + 7 = 64 (even)

isAlpha("True") ➞ true
// 20 + 18 + 21 + 5= 64 (even)

isAlpha("alexa") ➞ false
// 1 + 12 + 5 + 24 + 1= 43 (odd)

Notes

• Case insensitive.
• Ignore non-letter symbols.