substr static method
Returns a substring of value starting at start for length chars.
Implementation
static String substr(String value, int start, [int? length]) {
var s = start < 0 ? value.length + start : start;
if (s < 0) s = 0;
if (s > value.length) return '';
final end = length == null
? value.length
: (s + length).clamp(s, value.length);
return value.substring(s, end);
}