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substring abstract method
String substring(Returns the substring of this string that extends from startIndex, inclusive, to endIndex, exclusive.
var string = 'dartlang';
string.substring(1);    // 'artlang'
string.substring(1, 4); // 'art'
  Source
String substring(int startIndex, [int endIndex]);
  © 2012 the Dart project authors
Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
 https://api.dartlang.org/stable/1.24.3/dart-core/String/substring.html