Returns the character at the specified index of a String object.
function charAt(index : Number) : String
Required. Zero-based index of the desired character. Valid values are between 0 and the length of the string minus 1.
The charAt method returns a character value equal to the character at the specified index. The first character in a string is at index 0, the second is at index 1, and so forth. Values of index out of valid range return an empty string.
The following example illustrates the use of the charAt method:
var str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var s = str.charAt(n - 1);