有人會解釋這個代碼的字符？

Question

我一直在試圖解決一個計算字符串中的字符的難題，並找到以下代碼。代碼工作，但我無法理解替換部分：

function getCharCounts(s) { 
    var letters = {}; 
    s.replace(/\S/g, function(s){ 
     letters[s] = (isNaN(letters[s] ? 1 : letters[s]) + 1); 
    }); 

    return letters; 
} 

console.log(getCharCounts('he111 144pressions'));​ 

會有人請解釋一下代碼給我或寫一個簡單的版本？

Answer 1

function getCharCounts(s) { 

    // This variable will be visible from inner function. 
    var letters = {}; 

    // For every character that is not a whitespace ('\S') 
    // call function with this character as a parameter. 
    s.replace(/\S/g, function(s){ 

     // Store the count of letter 's' in 'letters' map. 
     // On example when s = 'C': 
     // 1. isNaN checks if letters[c] is defined. 
     //  It'll be defined if this is not a first occurrence of this letter. 
     // 2a. If it's not the first occurrence, add 1 to the counter. 
     // 2b. If it's the first occurrence, assigns 1 as a value. 
     letters[s] = (isNaN(letters[s]) ? 1 : letters[s] + 1); 
    }); 

    return letters; 
} 

注：括號isNaN（）是錯誤的。上面的代碼已更正。

Answer 2

這裏有一個簡單的例子：

function getCharCounts(s) { 
    var letters = {}; 
    var is_not_whitespace = /\S/; 

    // Iterate through all the letters in the string 
    for (var i = 0; i < s.length; i++) { 
     // If the character is not whitespace 
     if (is_not_whitespace.test(s[i])) { 
      // If we have seen this letter before 
      if (s[i] in letters) { 
       // Increment the count of how many of this letter we have seen 
       letters[s[i]]++; 
      } else { 
       // Otherwise, set the count to 1 
       letters[s[i]] = 1; 
      } 
     } 
    } 

    // Return our stored counts 
    return letters; 
}