Returns a substring beginning at a specified location and having a specified length.
function substr(start : Number [, length : Number]) : String
Required. The starting position of the desired substring. The index of the first character in the string is zero.
Optional. The number of characters to include in the returned substring.
If length is zero or negative, an empty string is returned. If not specified, the substring continues to the end of the string.
The following example illustrates the use of the substr method.
var s = "The quick brown fox jumps over the lazy dog.";
var result = s.substr(10, 5);
// Returns "brown".