为什么迭代循环太多？

Question

I am trying to loop through the object matches for the value of matchId however when i use the loop when the match.length = 2 then console.log(i) returns 8 times?

here is my code:

lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function(err, matches) {
    for (var matchId in matches) {
      var game = matches.matches;

      for(var i = 0; i < game.length; i++) {
        console.log(i);
      }
    }
  });

the return of the object is as follows:

{ matches: 
[ { region: 'OCE',
   platformId: 'OC1',
   matchId: 122934310,
   champion: 36,
   queue: 'TEAM_BUILDER_DRAFT_RANKED_5x5',
   season: 'SEASON2016',
   timestamp: 1456100362493,
   lane: 'BOTTOM',
   role: 'DUO_SUPPORT' },
 { region: 'OCE',
   platformId: 'OC1',
   matchId: 122510663,
   champion: 44,
   queue: 'TEAM_BUILDER_DRAFT_RANKED_5x5',
   season: 'SEASON2016',
   timestamp: 1455751169038,
   lane: 'BOTTOM',
   role: 'DUO_SUPPORT' } ],
startIndex: 0,
endIndex: 2,
totalGames: 135 }

thanks guys

Answer 1

It seems that your nested for loop within your foreach is going to trigger this as you'll iterate matches.length * match.games.length :

// This will iterate for each match
for (var matchId in matches) {
    // Is this intentional (should this be matchId.matches?)
    var game = matches.matches;
    // This will iterate for each game (in each match)
    for(var i = 0; i < game.length; i++) {
       console.log(i);
    }
}

So if you have two matches and your loop iterates eight times, this means that there was eight games between your two match objects.

Answer 2

Your for (var matchId in matches) loop (a for...in loop ) is looping the property keys of the return object, which means the following keys are being looped ['matches', 'startIndex', 'endIndex', 'totalGames'] , ie 4 times.

And then the inner loop is repeating your return object's matches array (2 members), and thus 4*2 = 8 .

If you want to log the matchIds, what you want to do is perhaps this:

lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function(err, matches) {
  var gameMatches = matches.matches;

  for(var i = 0; i < gameMatches.length; i++) {
    console.log(gameMatches[i].matchId);
  }
});

Or do it more functionally (does not work in Internet Explorer 8):

lolapi.MatchList.getBySummonerId(obj['savisaar2'].id, options, function(err, matches) {
  matches.matches.forEach(function(gameMatch){
      console.log(gameMatch.matchId);
  });
  // Outputs:
  // 122934310
  // 122510663
});