Dart array util methods

dart_array_util_methods_exam.dart

void main(){
  var data = [1, 2, 3, 4, 5];
  
  //forEach
  print('forEach1');
  var eachData = data.forEach((value) { 
    print(value);
    return value;
  });
  //print(eachData); //eachData is void.
  
  //map
  var strData = data.map((value) {
    print('num $value');
    return value+1;
  });
  print('map : $strData');

  //List.from
  var copyData = List.from(data);
  print('copy : $copyData');
  
  //sort
  var sorted = List.from(data);
  sorted.sort((n1, n2) => n2-n1);
  print('sort : $sorted');
    
  //reduce
  var sum = data.reduce((curr, next) => curr+next);
  print('reduce : $sum');
  
  //fold
  var initialValue = 10;
  var sum2 = data.fold(initialValue, (curr, next) => curr + next);
  print('fold : $sum2');
  
  //every
  var is1AndOver = data.every((num)=> num>=1);
  print('every 1 : $is1AndOver');
  var is2AndOver = data.every((num)=> num>=2);
  print('every 2 : $is2AndOver');
  
  //where
  var over2s = data.where((num) => num>=2);
  print('where 2 : $over2s');
  
  //firstWhere
  var over3 = data.firstWhere((num) => num>=3);
  print('firstWhere 3 : $over3');
  var over6_orElse = data.firstWhere((num) => num>=6, orElse:()=>null);
  print('firstWhere 6_orElse : $over6_orElse');
  
  //singleWhere
  /*
   * var under3 = data.singleWhere((num) => num<3, orElse:()=>null);
   * print('singleWhere under3 : $under3');
  */
  var under2 = data.singleWhere((num) => num<2, orElse:()=>null);
  print('singleWhere under2 : $under2');
  
  //take,skip
  var takeData = data.take(3);
  print('take : $takeData');
  var skipData = data.skip(2);
  print('skip : $skipData');
  var takeSkipData = data.take(3).skip(1);
  print('takeSkip : $takeSkipData');
  var takeSkipTakeData = data.take(3).skip(1).take(1);
  print('takeSkipTakeData : $takeSkipTakeData');
  
  //expand
  var doubleData = [data, data];
  var flatDoubleData = doubleData.expand((pair) => pair);
  print('expand : $flatDoubleData');
  var duplicated = data.expand((num) => [num, num]);
  print('expand2 : $duplicated');
        
}