JS: String Index
Index of String
Many string methods take index (integer) as argument, or return a index.
Some string methods also allow negative index. Negative index usually means count from right to left, starting at the end of string, but some method treat negative index as 0.
a b c d e f g 0 1 2 3 ... -1
The most intuitive way to understand index is to think of index as between the chars. Index 0 is before first character. Index 1 is after first character. Index -1 is the place between last character and second last character.