Pythonic dictionary in Javascript

Question

How would you implement pythonic dictionary in Javascript that is able to store key value pairs and key can be tuple?

I'd like to find all anchors and then store values of it's href and title attributes to dictionary as keys (href value, title value) and number of occurrencies of this tuple as a value.

The code would look like this (it's a mix of Python and Javascript):

var anchors = document.querySelectorAll ("a");
d = []; // dictionary data structure
for (var i = 0, len = anchors.length; i < len; i++) {
  currentTuple = (anchors[i].href, anchors[i].title);
  if (!d.containsKey(currentTuple)) {
    d[currentTuple] = 1;
  } else {
   d[currentTuple] += 1;
  }
}

Maybe it would be easier if keys couldn't be tuples, but if it's possible i'd like to see it.

thank you

This library I've found quite useful for this purpose: timdown.co.uk/jshashtable. If you implement a custom .equals function, it should work for your needs. — pimvdb
– pimvdb, Commented Dec 17, 2011 at 13:01

Esailija · Accepted Answer · 2011-12-17 13:06:24Z

1

Could this work? It just concatenates title and href as a unique key.

var data = [].reduce.call( document.links, function( data, a){
    var key = a.href+","+a.title;
    if( data[key] ) {
        data[key]++;
    }
    else {
        data[key] = 1;
    }   

return data;
}, {} );

http://jsfiddle.net/knYwb/

answered Dec 17, 2011 at 13:06

Esailija

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17 Comments

hugomg Over a year ago

You might need to use a different special character or excape commas in the title in order to guarantee uniqueness

Esailija Over a year ago

@missingno, what do you mean? the comma isn't even necessary for that it's just for readability when you dump the object in console.

hugomg Over a year ago

The problem is that when you concatenate you can theoretically have two separate tuples that generate the same key.

Esailija Over a year ago

@missingno, yes and then you increment the occurrence of that key by one. It has same title+href combination as a one that already exists.

Esailija Over a year ago

@xralf you would just loop through the data object and see which values are highest and then split their keys by , if you're using , as a separator.

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