Tally occurrences of a string in an array?

**jlizarraga** · 09-28-2008, 06:06 AM

Hi all,

I have an alphabetically sorted array of names, like this:

Code:

var someArray = new Array("Bob", "Bob", "John", "Steve");

I don't know what the names are going to be each time, and I want to output a list of the names with the number of occurrences next to the name, like this:

Bob (2)
John (1)
Steve (1)

Any tips greatly appreciated!

**Twey** · 09-28-2008, 07:35 AM

Code:

if (!Array.prototype.indexOf)
  Array.prototype.indexOf = function(elt /*, from*/) {
    var len = this.length,
        from = +arguments[1] || 0;

    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);

    if (from < 0)
      from += len;

    for (; from < len; ++from)
      if (from in this && this[from] === elt)
        return from;

    return -1;
  };

Array.prototype.count = function(elt) {
  for (var r = 0, c = -1; (c = this.indexOf(elt, c + 1)) > -1; ++r);
  return r;
};

**jscheuer1** · 09-28-2008, 10:46 AM

But how could we use that? Perhaps:

Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

<style type="text/css">
#result {
font: normal 90% sans-serif;
}
</style>

<script type="text/javascript">
if (!Array.prototype.indexOf)
  Array.prototype.indexOf = function(elt /*, from*/) {
    var len = this.length,
        from = +arguments[1] || 0;

    from = (from < 0)
         ? Math.ceil(from)
         : Math.floor(from);

    if (from < 0)
      from += len;

    for (; from < len; ++from)
      if (from in this && this[from] === elt)
        return from;

    return -1;
  };

Array.prototype.count = function(elt) {
  for (var r = 0, c = -1; (c = this.indexOf(elt, c + 1)) > -1; ++r);
  return r;
};

Array.prototype.removeDuplicates = function (deep) {
  deep = deep || 0; var is = function(i){return i? i : i === 0?  '0' : false;};
  for(var i = 0; i < this.length; ++i)
    for(var j = this.length-1; j > i; --j)
      if((is(this[i][deep]) || this[i]) == (is(this[j][deep]) || this[j]))
        this.splice(j, 1);
};


Array.prototype.enumerateEntries = function () {
 for(var c = [], i = 0; i < this.length; ++i)
  c.push(this[i] + ' (' + this.count(this[i]) + ')');
 c.removeDuplicates();
 return c;
};

var someArray = new Array("Bob", "Bob", "John", "Steve");

window.onload = function(){
document.getElementById('result').appendChild(document.createTextNode(someArray.enumerateEntries().join('\x0a\x0d')));
};
</script>
</head>
<body>
<div>
<pre id="result"></pre>
</div>
</body>
</html>

**jscheuer1** · 09-28-2008, 04:26 PM

But a much simpler approach to getting the data would be:

Code:

Array.prototype.enumerate = function(){
for(var o = {}, i = 0; i < this.length; ++i)
o[this[i]] = o[this[i]]? ++o[this[i]] : 1;
return o;
};

Which could be formatted more or less as before, or using this more elaborate and better looking method:

Code:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<style type="text/css">
#result {
font: normal 90% sans-serif;
}
#result .rhspan {
float: right;
}
#result br {
clear: right;
}
</style>
<script type="text/javascript">
Array.prototype.enumerate = function(){
for(var o = {}, i = 0; i < this.length; ++i)
o[this[i]] = o[this[i]]? ++o[this[i]] : 1;
return o;
};

function displayResults(ar, el){
el = document.getElementById(el);
while (el.lastChild) el.removeChild(el.lastChild);
var o = ar.enumerate(), p, s0, s1, br, w = 0;
for (p in o){
w = Math.max( w, (p + o[p]).length + 3 );
s0 = document.createElement('span');
s1 = document.createElement('span');
br = document.createElement('br');
s1.className = 'rhspan';
s0.appendChild(document.createTextNode(p));
s1.appendChild(document.createTextNode('(' + o[p] + ')'));
el.appendChild(s1);
el.appendChild(s0);
el.appendChild(br);
};
el.style.width = w + 'ex';
};

var someArray = new Array("Bob", "Twey", "Bob", "Twey", "John", "Mary", "Steve", "Mary", "Twey", "A real long name here", 0, 0, 257);
</script>
</head>
<body>
<div>
<input type="button" value="Go!" onclick="displayResults(someArray, 'result');">
<div id="result">
Results Will Appear Here
</div>
</div>
</body>
</html>

**jlizarraga** · 09-29-2008, 12:44 AM

Thank you both, this is exactly what I needed.

Thread: Tally occurrences of a string in an array?

Thread Tools

Search Thread

Tally occurrences of a string in an array?

The Following User Says Thank You to Twey For This Useful Post:

The Following User Says Thank You to jscheuer1 For This Useful Post:

Bookmarks

Bookmarks

Posting Permissions