"abcdefg".substr(3, 5)
defg
"abcdefg".substr(0, -2)
abcde
"abcdefg".substr(1, -2)
bcdef
"abcdefg".substr(2, -2)

"abcdefg".substr(1, -4)
bcd
"abcdefg".substr(1, -Infinity)

"abcdefg".substr(2, -1)

"abcdefg".substr(2, 9)
cdefg
"abcdefg".substr(0, -3)
abcd
"abcdefg".substr(2, -7)

"abcdefg".substr(5, -10)

