抽奖

lucky-draw.js

const AsciiTable = require("ascii-table");

class LuckyDraw {

    constructor(gifts) {
        this.gifts = gifts;
    }

    analyzeOdds() {
        const totalOfPriority = this.gifts.reduce((memo, gift) => memo + gift.priority, 0);
        return this.gifts.map(({name, quantity, priority}) => {
            const odds = priority / totalOfPriority * 100;
            return {
                name,
                quantity,
                priority,
                odds
            }
        });
    }

    luck() {
        const remainingGifts = this.gifts.filter(gift => gift.quantity !== 0);
        const totalOfPriority = remainingGifts.reduce((memo, gift) => memo + gift.priority, 0);
        const randomNumber = ~~(Math.random() * totalOfPriority);

        let priority = 0, luckyGift = null;
        remainingGifts.some((gift) => {
            priority += gift.priority;
            if (priority < randomNumber) {
                return false;
            }
            luckyGift = gift;
            if (luckyGift.quantity > 0) {
                luckyGift.quantity--;
            }
            return true;
        });

        return luckyGift;
    }

}


var luckyDraw = new LuckyDraw([
    {
        name: '1000',
        quantity: 1,
        priority: 1
    },
    {
        name: '100',
        quantity: -1,
        priority: 100
    },
    {
        name: '50',
        quantity: -1,
        priority: 200
    },
    {
        name: '30',
        quantity: -1,
        priority: 300
    },
    {
        name: '20',
        quantity: -1,
        priority: 300
    },
    {
        name: '10',
        quantity: -1,
        priority: 99
    }
]);

const comparator = (a, b) => parseFloat(b) > parseFloat(a);

const analyzedOdds = luckyDraw.analyzeOdds();

let table = new AsciiTable();
table.setHeading('Name', 'Quantity', 'Priority', 'Odds')
    .setAlign(1, AsciiTable.RIGHT)
    .setAlign(2, AsciiTable.RIGHT)
    .setAlign(3, AsciiTable.RIGHT);
analyzedOdds.forEach(({name, quantity, priority, odds}) => {
    table.addRow(name, quantity, priority, odds + '%');
});
table.sortColumn(3, comparator);
console.log(table.toString());


let totalOfCount = 0;
const countByName = {};
for (let i = 0; i < 2000; i++) {
    const {name} = luckyDraw.luck();
    if (!countByName.hasOwnProperty(name)) {
        countByName[name] = 0;
    }
    countByName[name]++;
    totalOfCount++;
}

table = new AsciiTable();
table.setHeading('Name', 'Quantity', 'Odds', 'Offset')
    .setAlign(1, AsciiTable.RIGHT)
    .setAlign(2, AsciiTable.RIGHT)
    .setAlign(3, AsciiTable.RIGHT);
const names = Object.keys(countByName);
names.forEach((key) => {
    const count = countByName[key];
    const odds = count / totalOfCount * 100;
    const {odds: expectedOdds} = analyzedOdds.find(({name}) => name === key);
    const offset = expectedOdds - odds;
    table.addRow(key, count, odds + '%', offset + '%');
});
table.sortColumn(1, comparator);
console.log(table.toString());