In most cases, a sorting function is a best tool to make a ranking. But how about tie scores? You may end up with giving different ranks for tie scores. And I'm quite sure that will make your users dissatisfied.
Solution? You are on the right page.
This module provides various ranking strategies to assign correct ranks to tie
scores. It comes with 5 most common strategies:
competition, modified-competition, dense, ordinal, and fractional.
npm install ranked
Suppose we want to rank an array of computer languages by the year they were introduced.
const languages = [
{ name: 'Javascript', year: 1995 },
{ name: 'Java', year: 1995 },
{ name: 'C#', year: 2001 },
{ name: 'Groovy', year: 2003 },
{ name: 'Scala', year: 2003 },
{ name: 'Go', year: 2009 },
];
We need to provide a function defining the sorting criteria. The function must accept one entry of the array and returns a value to rank on (the year in this case). Note the returned value can be directly an attribute of the object, or any computed value based on that object (e.g. the math test score plus the English test score of a student).
const scoreFn = language => language.year;
Let's run the ranking operation on this list of languages
const ranked = require('ranked');
const rankedLanguages = ranked.ranking(languages, scoreFn);
The rankedLanguages is an array that looks like below. By default, it sorts
by descending order, using the competition strategy, and starts ranking at 1
[ { rank: 1, item: { name: 'Go', year: 2009 } },
{ rank: 2, item: { name: 'Groovy', year: 2003 } },
{ rank: 2, item: { name: 'Scala', year: 2003 } },
{ rank: 4, item: { name: 'C#', year: 2001 } },
{ rank: 5, item: { name: 'Javascript', year: 1995 } },
{ rank: 5, item: { name: 'Java', year: 1995 } } ]
To change the ranking strategy, use the third optional parameter.
const rankedLanguages = ranked.ranking(items, scoreFn, { strategy: 'dense' });
To sort in ascending order
const rankedLanguages = ranked.ranking(items, scoreFn, { reverse: true });
To start ranking at any number (e.g. 5).
const rankedLanguages = ranked.ranking(items, scoreFn, { start: 5 });
// Go language would have a rank of 5.