CODEWITHSUNDEEP
javascript
Vget98
Vget98

Reputation: 15

Letter count function javascript

Hi I have a quick question

I am trying to make a function that takes a string input "aacbdgtg" and have it output an array like so:

[["a", 2], ["c", 1], ["b", 1], ["d", 1], ["g", 2], ["t", 1]]

So far I have written 

var hist = function(string) {
  var result = [];

  for(var i = 0; i < string.length; i++) {
    if (result.length === 0) {
      result.push([string[i], 1]);
    }
    else {
      for (var j = 0; j < result.length; j++) {
        if (string[i] === result[j][0]) {
          result[j][1]++;
        }
      }
      result.push([string[i], 1]);
    }
  }
  return result;
};

And i get a result of 

[["a", 2], ["a", 1], ["c", 1], ["b", 1], ["d", 1], ["g", 2], ["t", 1], ["g", 1]]

Any help would be great thank you as I cam stuck and need help, I am not sure how to check if an array already has another array with the same letter

For example I don't know how to check if [["a", 2], ["a", 1]] has already used the letter "a"

Upvotes: 0

Views: 171

Answers (1)

Pranav C Balan
Pranav C Balan

Reputation: 115222

Better way is to create an object first afterwards create the array structure using it. Also you can use reduce() method here.

var hist = function(str) {
  var result = [],
    temp;

  // generate the object which holds string count
  temp = str.split('').reduce(function(a, b) {
    a[b] = a[b] + 1 || 1;
    return a;
  }, {});

  // generate the result using the object
  var result = Object.keys(temp).map(function(v) {
    return [v, temp[v]];
  });

  return result;
};

document.write('<pre>' + JSON.stringify(hist('aacbdgtg')) + '</pre>');
Check reduce method polyfill option for old browsers.

Of using simple for loop only

var hist = function(str) {
  var result = [],
    temp = {},
    strArr = str.split('');

  // generate the object which holds string count
  for (var i = 0; i < strArr.length; i++) {
    temp[strArr[i]] = temp[strArr[i]] + 1 || 1;
  }

  // generate the result using the object
  var keys = Object.keys(temp);
  for (var i = 0; i < keys.length; i++) {
    result.push([keys[i], temp[keys[i]]]);
  }

  return result;
};

document.write('<pre>' + JSON.stringify(hist('aacbdgtg')) + '</pre>');

Upvotes: 2

Related Questions