使用Javascript具有两个参数的非递归函数

Question

I am trying to create a function with two parameters that will count how times a character repeats in a given string. I have my code below but it is not working properly. Also, I am trying to make it a non-recursive function. Can anyone help me with that?

function count(char,word) {
  var a,b;
  a= char
  b= word
  c= b.indexof(a)
  return c
}

count('a','apple')

Answer 1

To count the occurrences of a string inside another one, you can split the latter using the former as the separator, and then use length to count the items of the returned array.

function count(char, word) {
  return word.split(char).length - 1;
}

Answer 2

If what you mean by your question is "how many occurrences of a given character are there in a word", then there are several possibilities. You can loop calling .indexOf() , you can let a regex find all the matches or you can just iterate through the string manually comparing.

If you meant something different by your question, please clarify the question.

Here are some possibilities:

 function count(char, word) { var cntr = 0; var pos = 0; while ((pos = word.indexOf(char, pos)) !== -1) { ++cntr; ++pos; } return cntr; } var cnt = count('a','apple'); document.write(cnt + "<br>"); cnt = count('p','apple'); document.write(cnt);

Or, you could use a regex if your character is not a special regex character:

 function count(char, word) { var cnt = word.match(new RegExp(char, "g")); return cnt ? cnt.length: 0; } var cnt = count('p', 'apple'); document.write(cnt);

Or, you could just iterate through the string and manually count:

 function count(char, word) { var cnt = 0; for (var i = 0; i < word.length; i++) { if (word.charAt(i) === char) { ++cnt; } } return cnt; } var cnt = count('p', 'apple'); document.write(cnt);

Answer 3

This is a very simple loop that iterates through the word , counting the instances of ch .

function count(ch,word) {
  var i,count = 0;
  for(i = 0; i < word.length; i++) {
    if (word[i] === ch) count++;
  }
  return count;
}

console.log(count('p','apple'));

Answer 4

You need loops:

 function count(c, word) { var i = 0; var arr = word.split(''); //break into array var a; while (arr.length) { //until array runs out of letters a = arr.pop(); // pull out one by one if (a === c) // got match i++; } return i; } alert(count('a', 'apple'));

Answer 5

The simplest way would probably be just looping through the input. Like this:

function count(char,word) {
  var count = 0;
  for(var i = 0; i < word.length; i++)
  {
    if(word.charAt(i) === char)
      count++;
  }
  return count;
}

Answer 6

Here's a way you can do this with a regular expression:

function countLetter(letter,word) {
  var regexp = New RegExp(letter, 'g') //searches word for letter
  var arr = word.match(regexp);        //finds the letter within the word,
  return arr == null ? 0 : arr.length;
}                                      //sticks that letter into arr for each time it
                                       //appears in the word

console.log(countLetter('a','apple a a a '));
//arr = ['a', 'a', 'a', 'a'], arr.length = 4
console.log(countLetter('p','apples'));
//arr = ['p','p'] arr.length = 2

Hope this helps!

Answer 7

I would go with an accumulator function for simply counting occurrences

function count(char,word) {
    return [].reduce.call(word,function(p,c){
        return p += char == c ? 1 : 0;
    },0);
}

However, that would just be for totals. In order to count "in a row" is much different and would require tracking the repetitions

function count(char,word) {
    var total = 0;
    var max = 0;
    [].reduce.call(word.substr(1,word.length),function(p,c){
        if(p == c && c == char){ total++ }else{
            if( total > max ) max = total;
            total = 0;
        }
        return c;
    },word[0]);
    return max > 0 ? max + 1 : 0;
}