Question

出于某种原因，我无法理解此代码中的内容

function mode(arr){
  var modecount = {}; // creating an object to add number and its mode
  for(var i = 0; i < arr.length; i++){ //iterating through array
    if(!modecount[arr[i]]){ /*This part I don't understand what do these two lines mean?
    I interpret it as if the current number in the array doesn't equal a number already
    in the modecount object then it equals 0 */
      modecount[arr[i]] = 0;
    }
    modecount[arr[i]] += 1; /* also what is happening here it is adding 1 to the value
    of modecount but why does it not add 1 to unique numbers and how does the code know
    to add 1 if it finds duplicates? */
    }
  return modecount;
}
mode([3,4,3,43,4,34,34,3,3,3,3,3]);

似乎我已经盯着这段代码好几个小时而且无法得到它。请有人向我解释，就像我3岁那样。

Answer 1

它基本上计算传递的数组中特定值的存在时间，但基值为0时，首先出现该值以初始化该值的属性。

尽管modecount被指定为对象，但是以可变方式访问对象属性的方式是使用括号表示法。

的输出

mode([3,4,3,43,4,34,34,3,3,3,3,3]);

将是：

{ 3: 7, 4: 2, 43: 1, 34: 2 }

Answer 2

我假设第一部分只是简写，以检查modecount[arr[i]]是否已初始化/定义。如果它返回“falsey”值，则表示未初始化（访问modecount[arr[i]]返回undefined）或者值为0 - 后者不可能，因为下一行总是立即将0增加到1.

请注意，您可以将此检查替换为if(typeof(modecount[arr[i]]) === "undefined")，以获得等效和更明确的行为。

关于函数的整体操作，请考虑以下pesudocode：

var modecount = {}

foreach element in array:
    if modecount[element.value] is not defined:
        modecount[element.value] = 0

    modecount[element.value]++

Answer 3

我希望这会有所帮助。我重写了几个变量，因为我感觉它读得更好。

function mode(arr){

  // create an index for our counter
  var index = {};

  // a normal for-loop to iterate through the passed in numbers
  for(var i=0, num; i<arr.length; i++){

    // each time the foor loop runs, set num to arr[i]
    num = arr[i];

    // if no valid counter was found...
    if(!index[num]){

      // then create a new counter; initialize to 0
      index[num] = 0;
    }

    // add 1 to the counter
    index[num] += 1;
  }

  // return the counters
  return index;
}

mode([3,4,3,43,4,34,34,3,3,3,3,3]);

Answer 4

以下是高级别的解释：

这是一个数字列表，它计算每个数字出现在该列表中的次数。

现在，这是内联解释：

function mode(arr){

  // Initialize an object literal 
  var modecount = {};

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

    // If the value of arr[i] does NOT exist in the object modecount
    if (!modecount[arr[i]]) { 

      // Set the count of arr[i] to zero
      // Why? Because it if doesn't exist
      // then doing modecount[arr[i]] += 1 will throw an error
      // because modecount[arr[i]] will be undefined. 
      modecount[arr[i]] = 0;
    }

    // We increase the count of arr[i] in modecount by 1.
    // You asked about duplicates. 
    // It handles duplicates fine because modecount 
    // acts as a hash map (every key is unique). 
    // Doing modecount[5] over and over will 
    // give you the same value associated with 5.
    modecount[arr[i]] += 1;
    }

  return modecount;
}
// Call the function with our array
mode([3,4,3,43,4,34,34,3,3,3,3,3]);

我认为这个逻辑虽然正确，但可以改进。在第一个IF语句之后赋值为0会降低清晰度。如果它不存在，为什么设置为零？只有在我阅读了接下来的几行之后才有意义。

以下是我将如何重写它：

function mode(arr) {
    var modeCount = {};

    for (var i = 0; i < arr.length; i++) {
        // Save the value so we don't have to do arr[i] every time
        var currMode = arr[i];
        // If it exists
        if (modeCount[currMode]) {
            // Increment by 1
            modeCount[currMode]++;
        } else {
            // Otherwise, it's the first one
            modeCount[currMode] = 1;
        }
    }

    return modeCount;
}

console.log(mode([3, 4, 3, 43, 4, 34, 34, 3, 3, 3, 3, 3]))

Answer 5

该函数循环传递的数组，将每个事件编号存储为modecount对象上的number：count对。因此，当您的函数工作时，modecount对象将如下所示：

{}
{ 3: 1 }
{ 3: 1, 4: 1 }
{ 3: 2, 4: 1 }
{ 3: 2, 4: 1, 43: 1 }
{ 3: 2, 4: 2, 43: 1 }
and so on...

需要澄清这个代码我写的是找到一个数组的模式

5 个答案: