使用下劃線填充數組中缺少的對象

Question

我正在玩一個數據集，用於統計某人在某個小時內提交的提交數。我可以一個人做了一個承諾，他們多少次犯下的時間創建一個數組對象：

[ { hour: '6', commits: 2 }, 
    { hour: '7', commits: 6 }, 
    { hour: '8', commits: 6 }, 
    { hour: '9', commits: 4 }, 
    { hour: '10', commits: 4 }, 
    { hour: '11', commits: 6 }, 
    { hour: '12', commits: 18 }, 
    { hour: '13', commits: 18 }, 
    { hour: '14', commits: 14 }, 
    { hour: '15', commits: 30 }, 
    { hour: '16', commits: 24 }, 
    { hour: '17', commits: 18 }, 
    { hour: '18', commits: 24 }, 
    { hour: '19', commits: 22 }, 
    { hour: '20', commits: 6 }, 
    { hour: '21', commits: 16 }, 
    { hour: '22', commits: 8 } ] 

如果我堅持試圖填充缺失小時。所以在上面的例子中，我需要包括沒有提交任務的時間。我一整天都在使用0-24範圍。這是我希望得到的結果：

[ 
    { hour: '0', commits: 0 }, 
    { hour: '1', commits: 0 }, 
    { hour: '2', commits: 0 }, 
    { hour: '3', commits: 0 }, 
    { hour: '4', commits: 0 }, 
    { hour: '5', commits: 0 }, 
    { hour: '6', commits: 2 }, 
    { hour: '7', commits: 6 }, 
    { hour: '8', commits: 6 }, 
    { hour: '9', commits: 4 }, 
    { hour: '10', commits: 4 }, 
    { hour: '11', commits: 6 }, 
    { hour: '12', commits: 18 }, 
    { hour: '13', commits: 18 }, 
    { hour: '14', commits: 14 }, 
    { hour: '15', commits: 30 }, 
    { hour: '16', commits: 24 }, 
    { hour: '17', commits: 18 }, 
    { hour: '18', commits: 24 }, 
    { hour: '19', commits: 22 }, 
    { hour: '20', commits: 6 }, 
    { hour: '21', commits: 16 }, 
    { hour: '22', commits: 8 }, 
    { hour: '23', commits: 0 }, 
    { hour: '24', commits: 0 } 
] 

這裏是我用來創建這些對象的功能：

var getAuthorAndHourCounts = (groupedByAuthor) => { 

    var result = _.map(groupByAuthor, (value, key, list) => { 

    var author = key; 
    var hours = _.countBy(value, 'hour'); 

    var commitHourList = []; 

    _.each(hours, (v,k) => { 
     var obj = {}; 
     obj.hour = k; 
     obj.commits = v; 
     commitHourList.push(obj); 
    }); 

    return { 
     person: author, 
     times: commitHourList 
    }; 

    }); 
    return result; 
}; 

如何添加缺失的時代？我正在考慮創建一個列表（0-24），然後查看一個小時是否不在列表中，以便將零值添加到該對象中。不知道如何完成。

Answer 1

如何只初始化commitHourList使得它包含所有小時0提交，然後用實際數據填充它：

// initialize commitHourList with 24 objects 
// one for each hour and each with 0 commits 
var commitHourList = _.range(24).map((hour) => ({ hour, commits: 0 })); 

// for every received hour, add proper commits 
_.each(hours, (commits, hour) => { 
    commitHourList[hour].commits = commits; 
}); 

這樣一來，不管小時就不要添加會自動有0提交。

注：使用range然後map初始化數組是更少的代碼，但確實每次迭代陣列的兩倍。更高效的方法是在某個實用程序中創建該陣列一次，然後在每次需要新實用程序時複製該陣列。

例如：

// utility that creates the hours array when initialized 
// and returns a function that will return a copy of the hours array on each call 
var getHoursArray = (function() { 
    var arr = _.range(24).map((hour) => ({ hour, commits: 0 })); 
    return function() { 
    return arr.slice(); 
    } 
})(); 

，然後用它喜歡：

var commitHourList = getHoursArray(); 

使用slice通常是複製一個數組，但here are other possibilities