使用Javascript计算字符串的频率字母

Question

我一直在想出一个对这个练习的答案，但是在那里我看不到它。我将分享练习的描述，我的代码和最后的输出。

描述：

现在我们要拯救每个数组的长度最长的一个新的数组称为array_lengths

打开控制台，并重新加载索引页看到代码的结果。

编写一个函数charFreq（），该函数接受一个字符串并构建其中包含的字符的频率列表。

作为一个条件，你必须使用对象freqCounter。

将列出的频率表示为Javascript对象。用charFreq（“abbabcbdbabdbdbabababcbcbab”）来尝试。

CODE：

function charFreq(string) { 
 

 
    var array_lengths = []; 
 

 
    // compute frequencies of each value 
 
    for (var i = 0; i < string.length; i++) { 
 
    value = string[i]; 
 
    if (value in array_lengths) { 
 
     array_lengths[value] ++; 
 
    } else { 
 
     array_lengths[value] = 1; 
 
    } 
 
    } 
 

 

 
    // make array from the frequency object to de-duplicate 
 
    var freqCounter = []; 
 
    for (value in array_lengths) { 
 
    freqCounter.push(value); 
 
    } 
 

 
    // sort the uniques array in descending order by frequency 
 
    function compareFrequency(a, b) { 
 
    return array_lengths[b] - array_lengths[a]; 
 
    } 
 

 
    return freqCounter.sort(compareFrequency); 
 
} 
 

 
//OUTPUT: 
 

 
// if I had it right I should get "true" from every of the following values of the function but the point is that I'm getting all false...where's the error? 
 

 
counter = charFreq("abbabcbdbabdbdbabababcbcbab"); 
 

 
console.log(counter['a'] === 7); 
 

 
console.log(counter.b === 14); 
 

 
console.log(counter['c'] === 3);

Answer 1

两个问题

• 使用对象

  var array_lengths = {}; // object 
  

• 返回，如果没有排序和其它对象东西

  return array_lengths; 
  

function charFreq(string) { 
 
    var array_lengths = {}; // object 
 

 
    // compute frequencies of each value 
 
    for(var i = 0; i < string.length; i++) { 
 
     value = string[i]; 
 
     if(value in array_lengths) { 
 
      array_lengths[value]++; 
 
     } else { 
 
      array_lengths[value] = 1; 
 
     } 
 
    } 
 
    return array_lengths; 
 
} 
 

 
//OUTPUT: 
 
// if I had it right I should get "true" from every of the following values of the function but the point is that I'm getting all false...where's the error? 
 

 
counter = charFreq("abbabcbdbabdbdbabababcbcbab"); 
 
console.log(counter); 
 
console.log(counter['a'] === 7); 
 
console.log(counter.b === 14); 
 
console.log(counter['c'] === 3);

Answer 2

为此，您可以使用ES6 - 使用Set通过您的字符串转换成一个数组并通过整个事情new Set得到数组中的唯一项目

let string = 'abbabcbdbabdbdbabababcbcbab'; 
let unique = [...new Set(string)]; 

Answer 3

分解它。你需要迭代字符串的每个部分，对吧？将它分成一个阵列和一个对象创建为每个元素的计数器：

var counter = {}; 
var string = "abbabcbdbabdbdbabababcbcbab"; 
var stringArray = string.split(''); 
stringArray.forEach(function(character){ 
    if(!counter.hasOwnProperty(character)){ 
    counter[character] = 0; 
    } 
    counter[character]++; 
}); 
console.log(counter); 

Answer 4

你是usings数组作为对象 我离开VAR freqCounter = Object.keys(array_lengths);，因为它是从字符串的唯一的字符。但是，它在你描述的代码中对你没有任何帮助。

function charFreq(string) { 
 

 
    var array_lengths = {}; 
 
    var value; 
 
    // compute frequencies of each value 
 
    for (var i = 0; i < string.length; i++) { 
 
    value = string[i]; 
 
    if (value in array_lengths) { 
 
     array_lengths[value] ++; 
 
    } else { 
 
     array_lengths[value] = 1; 
 
    } 
 
    } 
 

 

 
    // make array from the frequency object to de-duplicate 
 
    var freqCounter = Object.keys(array_lengths); 
 

 
    // sort the uniques array in descending order by frequency 
 
    function compareFrequency(a, b) { 
 
    return array_lengths[b] - array_lengths[a]; 
 
    } 
 

 
    return array_lengths; 
 
} 
 

 
//OUTPUT: 
 

 
// if I had it right I should get "true" from every of the following values of the function but the point is that I'm getting all false...where's the error? 
 

 
counter = charFreq("abbabcbdbabdbdbabababcbcbab"); 
 
console.log(counter); 
 
console.log(counter['a'] === 7); 
 

 
console.log(counter.b === 14); 
 

 
console.log(counter['c'] === 3);