Returns the substring at the specified location within a string.
substring(start, end?)
start
The starting index of the desired substring.
end
The ending index. The substring includes the characters up to, but not including, the code unit indicated by end. If end is omitted, the code units from start through the end of the original string are returned.
A string.
"Green Day".substring(6)
"Day"
"Green Day".substring(0, 5)
"Green"