如何在Javascript中的多维数组中获取每个标题的最小数字

Question

如何在JavaScript中获得每个标题和一个数组中的最小数字？

我希望能得到的结果仅保持在每个标题中最低，如下所示，

 var result = [["Alex", "morning", 69],
               ["Terry", "morning", 127],
               ["Peter", "morning", 269]];

谢谢

var value_array = [["Alex", "morning", 69],
                   ["Alex", "night", 537],
                   ["Terry", "Afternoon", 141],
                   ["Terry", "MidNight", 327],
                   ["Terry", "morning", 127],
                   ["Peter", "morning", 269]];
// I hope to filter each title(value_array[][0]) the lowest number(value_array[][2]) 
//Like the lowest for Alex(Title) is 69(lowest number).
//And the lowest for Terry(Title) is 127(lowest Number).
//And the lowest for Peter(Title) is 269(lowest Number).

// this is the format I try, but not working
var result = [];
for (var i = 0; i < value_array.length; i++) {

    for (var u = 0; u < value_array.length; u++) {

         if (value_array[i][0] == value_array[u][0]) {

              const numbers_arr = value_array[i][2];
              const add_arr = (a, b) => a + b;
           result.push(((numbers_arr.reduce(add_arr))/value_array.length).toFixed(0));

         }
     }
}

Answer 1

您可以使用哈希表来查找重复的名称，然后比较值：

 const value_array = [["Alex", "morning", 69], ["Alex", "night", 537], ["Terry", "Afternoon", 141], ["Terry", "MidNight", 327], ["Terry", "morning", 127], ["Peter", "morning", 269]];


 const result = [], hash = {};

 for(const [name, time, value] of value_array) {
   if(hash[name]) {
     if(hash[name][2] > value) {
       hash[name][1] = time;
       hash[name][2] = value;
    }
  } else {
    result.push(hash[name] = [name, time, value]);
  }
}

 console.log(result);

或者，您可以按名称对数组进行排序，然后按降序值排序，然后筛选出所有重复的名称：

 const value_array = [["Alex", "morning", 69], ["Alex", "night", 537], ["Terry", "Afternoon", 141], ["Terry", "MidNight", 327], ["Terry", "morning", 127], ["Peter", "morning", 269]];

 value_array.sort(([nameA, , valueA], [nameB, , valueB]) =>
   nameA.localeCompare(nameB) ||
   valueA - valueB
);

 let dupe = "";
 const result = value_array.filter(([name]) => name !== dupe && (dupe = name));

 console.log(result);

Answer 2

使用reduce函数并创建一个对象，然后使用Object.values从该对象获取值

var value_array = [
  ["Alex", "morning", 69],
  ["Alex", "night", 537],
  ["Terry", "Afternoon", 141],
  ["Terry", "MidNight", 327],
  ["Terry", "morning", 127],
  ["Peter", "morning", 269],
  ["Peter", "morning", 20]
];

let m = value_array.reduce(function(acc, curr) {
 //check if the object has key by name Alex,Peter ..
 // if not then create a key by the name and assign the value to it
 // Ex {Alex:["Alex", "morning", 69]}
  if (acc[curr[0]] === undefined) {
    acc[curr[0]] = curr
  } else {
    // if it has a key then check the number & compare
    // if it is less the than the current then replace it 
    if (acc[curr[0]][2] > curr[2]) {
      acc[curr[0]] = curr
    }

  }
  return acc
}, {})

console.log(Object.values(m))