[Greedy Spy on next value] #Array #JavaScript

greed-spy.js

const pattern = 'abcdefgh';

for (const [currentChar, nextChar] of pattern.split('').reduce((acc,value,idx,arr)=>{const entry = [value]; if ( arr.length > idx + 1 ) entry.push(arr[idx+1]); acc.push(entry); return acc},[])) {
    console.log(currentChar,nextChar)
}
/**
a b
b c
c d
d e
e f
f g
g h
h undefined
**/