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Question

我想创建一个包含每个字母的2D数组。问题是，我只能创建一个包含所有字母的2D数组。我执行以下操作。

function groupAnimals(animals) {

  var sort = []
  var alphabet = 'abcdefghijklmnopqrstuvwxyz'
  var temp = []
  for(var i = 0; i < alphabet.length; i++){
    for(var j = 0; j < animals.length; j++){
      if(animals[j][0] == alphabet[i]){
        temp.push(animals[j])
      } 
  }

}
sort.push(temp)
return sort
}


console.log(groupAnimals(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupAnimals(['elephant', 'fish', 'horse', 'bird', 'flamingo', 'dog', 'ant' ]));

但输出是

[ [ 'bear', 'chicken', 'cat', 'dolphin', 'tiger' ] ]
[ [ 'ant', 'bird', 'dog', 'elephant', 'fish', 'flamingo', 'horse' ] ]

代替

[ ['bear'], ['chicken', 'cat], ['dolphin'], ['tiger'] ]
[ ['ant'], ['bird'], ['dog'], ['elephant'], ['fish', 'flamingo'], ['horse']]

我尝试过在字母表循环后先创建一个数组临时文件，然后再将动物的名字推给它，但这太手工了，浪费时间，如果没有这样的字符，就会有一个空数组。我想通过循环来做到这一点，但我不知道如何进行循环。

function groupAnimals(animals) {

  var sort = []
  var alphabet = 'abcdefghijklmnopqrstuvwxyz'
  for(var i = 0; i < alphabet.length; i++){
    var A = []
    var B = []
    var C = []
    var D = []
    var E = []
    var F = []
    var T = []
    for(var j = 0; j < animals.length; j++){
      if(animals[j][0] == 'a'){
        A.push(animals[j])
      } else if(animals[j][0] == 'b'){
        B.push(animals[j])
      } else if(animals[j][0] == 'c'){
        C.push(animals[j])
      } else if(animals[j][0] == 'd'){
        D.push(animals[j])
      } else if(animals[j][0] == 'e'){
        E.push(animals[j])
      } else if(animals[j][0] == 'f'){
        F.push(animals[j])
      } else if(animals[j][0] == 't'){
        T.push(animals[j])
      }
  }

}
sort.push(A)
sort.push(B)
sort.push(C)
sort.push(D)
sort.push(E)
sort.push(F)
sort.push(T)
return sort
}

结果是

[ [],
  [ 'bear' ],
  [ 'chicken', 'cat' ],
  [ 'dolphin' ],
  [],
  [],
  [ 'tiger' ] ]
[ [ 'ant' ],
  [ 'bird' ],
  [],
  [ 'dog' ],
  [ 'elephant' ],
  [ 'fish', 'flamingo' ],
  [] ]

最好使用数组和循环

Answer 1

简化为数组对象，其中的键是值数组中单词的第一个字母，然后使用Object.values将其转换回数组数组：

const groupAnimals = (animals) => {
  const sorted = animals.slice().sort();
  const groupedObj = sorted.reduce((a, word) => {
    const key = word[0];
    if (!a[key]) {
      a[key] = [];
    }
    a[key].push(word);
    return a;
  }, {});
  return Object.values(groupedObj);
};

console.log(groupAnimals(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupAnimals(['elephant', 'fish', 'horse', 'bird', 'flamingo', 'dog', 'ant']));

上面的方法可以工作，但是如果您担心规范不能正式保证属性顺序，则可以随后对数组进行排序：

const groupAnimals = (animals) => {
  const groupedObj = animals.reduce((a, word) => {
    const key = word[0];
    if (!a[key]) {
      a[key] = [];
    }
    a[key].push(word);
    return a;
  }, {});
  return Object.values(groupedObj)
    .sort((a, b) => a[0][0].localeCompare(b[0][0]));
};

console.log(groupAnimals(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupAnimals(['elephant', 'fish', 'horse', 'bird', 'flamingo', 'dog', 'ant']));

Answer 2

压榨SomePerformance的答案，并先将所有内容更改为小写，以防影响排序。

function groupStrings(strings) {
    return Object.values(strings.sort().reduce((a, str) => {
        const s = str.toLowerCase();
        const f = s[0];
        a[f] = a[f] ? [...a[f], s] : [s];
        return a;
    }, {}));
}

console.log(groupStrings(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupStrings(['chevrolet', 'buick', 'dodge', 'bmw', 'mercedes', 'jaguar', 'landrover', 'audi', 'volkswagen', 'cadilac', 'ford', 'toyota', 'tesla']));

编辑

这里有几种处理数组和仅用于循环的方法。注释中有解释：

function groupStrings(strings) {

    // first sort the array
    var sortedStrings = strings.slice().sort();

    // create the start of the 2d array with the first word
    var twoDArray = [[sortedStrings[0]]];

    for (var i = 1; i < sortedStrings.length; i++) {

        // get the last child array in the 2d array
        var currentArray = twoDArray[twoDArray.length-1];

        // if the first letter of the current string is equal to the first letter of a string in the current child array,
        // add the current string to the current child array
        if (sortedStrings[i][0] === currentArray[0][0]) {
            currentArray.push(sortedStrings[i]);
            currentArray = currentArray.sort();

        // otherwise create a new child array with the current string
        } else {
            twoDArray.push([sortedStrings[i]])
        }

    }
    
    return twoDArray;
};

console.log(groupStrings(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupStrings(['chevrolet', 'buick', 'dodge', 'bmw', 'mercedes', 'jaguar', 'landrover', 'audi', 'volkswagen', 'cadilac', 'ford', 'toyota', 'tesla']));

function groupStrings(strings) {

    var alphabet = 'abcdefghijklmnopqrstuvwxyz';
    var twoDArray = [];

    for (var i = 0; i < alphabet.length; i++) {

        // create a temporary array for all words starting with the current letter
        var letterArray = [];

        for (var j = 0; j < strings.length; j++) {

            // if the first letter of the current string is equal to the current letter,
            // add it to the letter array
            if (strings[j][0] === alphabet[i]) {
                letterArray.push(strings[j]);
            }
        }

        // if any strings were added, add the letter array to the 2d array
        if (letterArray.length) {
            twoDArray.push(letterArray);
        }
    }

    return twoDArray;
};

console.log(groupStrings(['bear', 'chicken', 'dolphin', 'cat', 'tiger']));
console.log(groupStrings(['chevrolet', 'buick', 'dodge', 'bmw', 'mercedes', 'jaguar', 'landrover', 'audi', 'volkswagen', 'cadilac', 'ford', 'toyota', 'tesla']));

如何在不知道JavaScript中数组长度的情况下创建2D数组？

2 个答案:

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