Question

我想知道是否存在与此相同的原生javascript代码：

function f(array,value){
    var n = 0;
    for(i = 0; i < array.length; i++){
        if(array[i] == value){n++}
    }
    return n;
}

Answer 1

为此目的可能有不同的方法。
你的for循环方法显然没有错位（除了它看起来多余的代码量）。
这是一些额外的在数组中获得某个值的方法：

使用Array.forEach方法：

var arr = [2, 3, 1, 3, 4, 5, 3, 1];

function getOccurrence(array, value) {
    var count = 0;
    array.forEach((v) => (v === value && count++));
    return count;
}

console.log(getOccurrence(arr, 1));  // 2
console.log(getOccurrence(arr, 3));  // 3

使用Array.filter方法：

function getOccurrence(array, value) {
    return array.filter((v) => (v === value)).length;
}

console.log(getOccurrence(arr, 1));  // 2
console.log(getOccurrence(arr, 3));  // 3

Answer 2

您可以使用reduce来实现目标：

Working example

var a = [1,2,3,1,2,3,4];

var map = a.reduce(function(obj, b) {
  obj[b] = ++obj[b] || 1;
  return obj;
}, {});

Answer 3

另一个选择是：

count = myArray.filter(x => x == searchValue).length;

Answer 4

这是我的解决方案，不使用其他对象，而使用reduce：

const occurrencesOf = (number,numbers) => numbers.reduce((counter, currentNumber)=> (number === currentNumber ? counter+1 : counter),0);
occurrencesOf(1, [1,2,3,4,5,1,1]) // returns 3
occurrencesOf(6, [1,2,3,4,5,1,1]) // returns 0
occurrencesOf(5, [1,2,3,4,5,1,1]) // returns 1

Answer 5

您也可以使用forEach

let countObj = {};
let arr = [1,2,3,1,2,3,4];

let countFunc = keys => {
  countObj[keys] = ++countObj[keys] || 1;
}

arr.forEach(countFunc);

// {1: 2, 2: 2, 3: 2, 4: 1}

Answer 6

您可能希望使用indexOf()功能查找并计算value

中的每个array

function g(array,value){
  var n = -1;
  var i = -1;
  do {
    n++;
    i = array.indexOf(value, i+1);
  } while (i >= 0  );

  return n;
}

Answer 7

const arr = ["a", "a", "a", "b", "b", "b", "b", "c", "c", "c"];
count = 0;

function countValues(array, countItem) {
  array.forEach(itm => {
    if (itm == countItem) count++;
  });
  console.log(`${countItem} ${count}`);
}
countValues(arr, "c");

Answer 8

let ar = [2,2,3,1,4,9,5,2,1,3,4,4,8,5];

const countSameNumber = (ar: any, findNumber: any) => {
    let count = 0;
    ar.map((value: any) => {
        if(value === findNumber) {
            count = count + 1;
        }
    })
    return count;
}


let set = new Set(ar);
for (let entry of set) {
    console.log(entry+":", countSameNumber(ar, entry));
}

计算相同值在javascript数组中出现的次数

8 个答案: