aureooms/js-collections-counter

import { NotImplementedError } from '@aureooms/js-error' ;
import { nlargest } from '@aureooms/js-heapq' ;

import counts from './counts' ;

export default function BaseCounter ( Map , Dict ) {

    const Counter = function ( iterable ) {

        this.container = new Map( ) ;

        if ( iterable !== null ) this.update( iterable ) ;

    } ;

    Counter.prototype = new Dict( ) ;

    Counter.fromkeys = function ( seq , value = null ) {

        throw new NotImplementedError( "Counter.fromkeys() is undefined.  Use Counter(iterable) instead." ) ;

    } ;

    Counter.prototype.get = function ( key ) {

        if ( this.has( key ) ) return this.container.get( key ) ;

        return 0 ;

    } ;

    Counter.prototype.elements = function* ( ) {

        for ( let [ key , count ] of this ) {

            while ( count --> 0 ) yield key ;

        }

    } ;

    Counter.prototype.increment = function ( key , amount = 1 ) {

        this.set( key , this.get( key ) + amount ) ;

    } ;

    Counter.prototype.decrement = function ( key , amount = 1 ) {

        this.increment( key , -amount ) ;

    } ;

    Counter.prototype.update = function ( iterable ) {

        for ( let key of iterable ) this.increment( key ) ;

    } ;

    Counter.prototype.add = function ( other ) {

        for ( let [ key , count ] of other ) this.increment( key , count ) ;

    } ;

    Counter.prototype.subtract = function ( other ) {

        for ( let [ key , count ] of other ) this.decrement( key , count ) ;

    } ;

    Counter.prototype.most_common = function ( n = this.len( ) ) {

        return nlargest( counts , n , this ) ;

    } ;

    return Counter ;

}