Question

I am working on a Javascript application and have run into a problem that I can’t solve. I have to write a function that takes a string and returns an object where the property names are characters and the values are how often that character appears in the string. What I have written so far is:

function getFrequencies(str) {
    var holder = str;
    var ticker = str;
    var i = 0;
    var j = 0;
    var result = [];

    while (i < holder.length && j < ticker.length) {
        if (holder.charAt(i) < ticker.charAt(j)) {
            i++;
        }
        else if (ticker.charAt(j) < holder.charAt(i)) {
            j++;
        }
        else {
            result.push(holder.charAt(i));
            i++;
            j++;
        }
    }

    return result;
}

If there is someone who can help me figure out how to make this work correctly and tell me what I am doing wrong I would greatly appreciate it.

Answer 1

function getFrequencies(str) {
  var obj = {}, i;
  for (i = 0; i < str.length; i++) {
    if (str.charAt(i) in obj) {
       obj[str.charAt(i)]++;
    } else {
       obj[str.charAt(i)] = 1;
    };
  }
  return obj;
}

Or

String.prototype.getFrequencies = function () {
  var obj = {}, i, c;
  for (i = 0; i < this.length; i++) {
    c = this.charAt(i); 
    if (c in obj) {
       obj[c]++;
    } else {
       obj[c] = 1;
    };
  }
  return obj;
}

// usage
var ret = "abcabcieefje".getFrequencies();