Stats Frequency

frequency.js

//var data = ['A', 'O', 'A', 'B', 'B', 'AB', 'B', 'B', 'O', 'A', 'O', 'O', 'O', 'AB', 'B', 'AB', 'AB', 'A', 'O', 'A'];
var data = ['A', 'O', 'A','A','A','A', 'A','A','A','A', 'A','A','A','A', 'A','A','A','A', 'A','A','A','A'];
var count = {}
data.forEach((d) => {
	count[d] = ((count[d] === undefined) ? 1 : (count[d]+1));
});
var addAll = (accumulator, currentValue) => accumulator + currentValue;
var len = Object.keys(count).map((r) => count[r]).reduce(addAll);
Object.keys(count).map((r) => {
 console.log((count[r]/len)*100); 
 return ({'#': r, '%': (count[r]/len)*100})
});
//95.45454545454545
//4.545454545454546

https://www.statisticshowto.datasciencecentral.com/how-to-make-a-frequency-chart-and-determine-frequency/