javascript - 如何使用 JavaScript 输出数组中出现的次数

Question

这里的目标是计算以下数组中出现的次数: [2,3,7,9,7,3,2]

例如，如果用户输入 7，则输出应为 [2, 4]，因为 7 出现在这两个索引处。到目前为止我所拥有的看起来像这样

    var arr1 = [2,3,7,9,7,3,2];
    printArray(arr1);
    var indexOfNum = findValueInArray(arr1, num);

    if (indexOfNum === -1) {
    console.log('%d was not found in the array of random integers.', num);
   }
    else {
    console.log('%d was found in the array of random integers at index %d',num, indexOfNum);
}

我的结果是:

    arr[0] = 2
    arr[1] = 3
    arr[2] = 7
    arr[3] = 9
    arr[4] = 7
    arr[5] = 3
    arr[6] = 2
    7 was found in the array of random integers at index 2

我知道我已经很接近了，但我不确定我到底忽略了什么。谢谢大家!

Answer 1

试试这个，

var arr1 = [2,3,7,9,7,3,2];

function occurance(array,element){
  var counts = [];
    for (i = 0; i < array.length; i++){
      if (array[i] === element) {  
        counts.push(i);
      }
    }
  return counts;
}

occurance(arr1, 2); //returns [0,6]
occurance(arr1, 7); //returns [2,4]