Question

我是JavaScript的新手，所以请帮我解决这个问题：我有数组，我想获得相同值的数量。我的阵列是：

 var arr = ["red", "blue", "green", "red", "red", "gray"];

我想输出3，因为我有3个元素为红色。

这是我到目前为止所做的：

var numberOfSameElements = 0;
var arr = ["red", "blue", "green", "red", "red", "gray"];
for(var i = 1 ; i <arr.length;i++){
if(arr[i] === arr[i-1]){
   numberOfSameElements++;  
 }
}

  console.log(numberOfSameElements);

我一直得到1.请告诉我我做错了什么。非常感谢你！

Answer 1

您可以将数组缩减为哈希映射，以确定每个单词的数量：

var words = ["red", "blue", "green", "red", "red", "gray"];
var wordCounts = words.reduce(function(counts, word) {
  counts[word] = (counts[word] || 0)++;
}, { });

console.log(wordCounts);

// >> {
//      red: 3,
//      blue: 1,
//      green: 1,
//      gray: 1
//    }

如果您想要复制的任何单词的名称，可以向下过滤原始数组：

var repeatedWords = words.filter(function(word) {
  return wordCounts[word] > 1;
});

console.log(repeatedWords);

// >> ['red']

Answer 2

在这里，您使用了一个循环并使用之前的值检查了当前值。但实际上你需要两个循环。

首先选择一个值。第二个将匹配所选择的值与所有其他值。我使用了found标志来检查是否已找到重复值。试试这种方式，

var numberOfSameElements = 0;
var found = false;
var arr = ["red", "blue", "green", "red", "red", "gray"];
for(var i = 0 ; i <arr.length;i++){
    for(var j = 0; j < arr.length; j++){
        if(arr[i] === arr[j] && i != j){
            if(!found){
                numberOfSameElements++;
                found = true;
            }
        }
    }
    found = false;
}

console.log(numberOfSameElements);

jsFiddle

Answer 3

如果要在阵列中找到重复的最大数量，首先必须统计它们。然后找到最大重复次数（fiddle）：

function getLargestNumberOfSame(arr) {
    var counterMap = arr.reduce(function (sameMap, item) { // create a map of same values
        if (!sameMap[item]) {
            sameMap[item] = 1;
        } else {
            sameMap[item]++;
        }

        return sameMap;
    }, {});

    var maxValues = Object.keys(counterMap).map(function(key) {  // turn the map into array of max values
        return counterMap[key];
    });

    return Math.max.apply(window, maxValues); // return the maximum value
}

Answer 4

 var numberOfSameElements = 1;
var arr = ["red", "blue", "green", "red", "red", "gray"];
arr = arr.sort();
var last;
for(var i = 0 ; i <arr.length -1 ;i++) {
    //console.log(arr[i],arr[i+1]);
if(arr[i] == arr[i+1]){
   numberOfSameElements++;
   last = arr[i];

 } else { 
    console.log(arr[i],"repert",numberOfSameElements,"times");
    numberOfSameElements=1;
   }

}
console.log(last,"repert",numberOfSameElements,"times");

如何在javascript数组中找到相等元素的数量

4 个答案: