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Comparator

Configurable Comparator similar to java.util.Comparator in Java 8

Tính đến 23-10-2019. Xem phiên bản mới nhất.

Script này sẽ không được không được cài đặt trực tiếp. Nó là một thư viện cho các script khác để bao gồm các chỉ thị meta // @require https://update.greasyfork.org/scripts/390752/743392/Comparator.js 

// ==UserScript==
// @name         Comparator
// @namespace    hoehleg.userscripts.private
// @version      0.4
// @description  Configurable Comparator similar to java.util.Comparator in Java 8
// @author       Gerrit Höhle
// @grant        none
// ==/UserScript==

/* jshint esversion: 6 */
const Comparator = (() => {
    'use strict';

    // internal functions
    const isMissing = obj => obj === null || typeof obj === "undefined";
    const compareValues = (a, b) => (a < b) ? -1 : ((a === b) ? 0 : 1);
    const compareByMissing = (a, b) => isMissing(a) ? (isMissing(b) ? 0 : 1) : (isMissing(b) ? -1 : null);

    /**
     * Basic compare function
     * @param {*} a - Object or value to compare
     * @param {*} b - Object or value to which to compare
     * @param {boolean} [missingFirst=false] - order of "undefined" and "null". true = first, false = last.
     * @returns "-1" for a < b, "0" for a === b or "1" for a > b
     **/
    const compare = (a, b, missingFirst = false) => {
        let result = missingFirst ? compareByMissing(b, a) : compareByMissing(a, b);
        if (result !== null) {
            return result;
        }

        if (typeof a === 'string' || a instanceof String) {
            return a.localeCompare(b);
        }

        return compareValues(a, b);
    };

    /**
     * Creates the compare-function bound to a Comparator.
     * @param {Comparator} cmparator - the Comparator the compare - function should belong to
     * @returns {Function} the compare(a, b) - function
     */
    const createCompareFunction = (comparator) => {
        /**
         * Compare function bound to a comparator.
         * When executed the current setup of the comparator is considered
         * @param {*} a - Object or value to compare
         * @param {*} b - Object or value to which to compare
         **/
        return (a, b) => {
            if (comparator.isAscending) {
                const tmp = a;
                a = b;
                b = tmp;
            }

            let result = comparator.isMissingFirst ? compareByMissing(b, a) : compareByMissing(a, b);

            for (let i = 0; !result && i < comparator.sortByFunctionsAndComparators.length; i++) {
                const accessorFnc = comparator.sortByFunctionsAndComparators[i];

                if (accessorFnc instanceof Comparator) {
                    result = accessorFnc.compare(a, b);
                } else {
                    result = compare(accessorFnc(a), accessorFnc(b), comparator.isMissingFirst);
                }
            }

            return result !== null ? result : compare(a, b, comparator.isMissingFirst);
        };
    };

    // private field accessor
    const _isReverse = Symbol("isReverse");
    const _accessorFunctions = Symbol("accessorFunctions");
    const _isMissingFirst = Symbol("isMissingFirst");
    const _compareFunction = Symbol("compareFunction");

    // export class
    return class Comparator {
        /**
         * @param {Array.<function|Compator>} sortByFunctionsAndComparators - accessor-functions or comparators to evaluate values to sort by
         */
        constructor(...sortByFunctionsAndComparators) {
            this[_accessorFunctions] = sortByFunctionsAndComparators;
            this[_isReverse] = false;
            this[_isMissingFirst] = false;
            this[_compareFunction] = createCompareFunction(this);
        }

        /**
         * @type {Array.<function|Compator>} - accessor-functions and/or comparators to evaluate values to sort by
         **/
        get sortByFunctionsAndComparators() {
            return [...this[_accessorFunctions]];
        }

        get isAscending() {
            return this[_isReverse];
        }

        get isDescending() {
            return !this.isAscending;
        }

        get isMissingFirst() {
            return this[_isMissingFirst];
        }

        get isMissingLast() {
            return !this.isMissingFirst;
        }

        /**
         * @type {Function} - the compare(a, b) - function that returns "-1" for a < b, "0" for a === b or "1" for a > b.
         * the funtion is setup by this Comparator
         **/
        get compareFnc() {
            return this[_compareFunction];
        }

        /**
         * Defines that "undefined" and "null" gets sorted to the begin
         **/
        setMissingFirst() {
            this[_isMissingFirst] = true;
            return this;
        }

        /**
         * Defines that "undefined" and "null" gets sorted to the end
         **/
        setMissingLast() {
            this[_isMissingFirst] = false;
            return this;
        }

        /**
         * Reverses the sort order from ascending to descending and vice versa
         **/
        reverse() {
            this[_isReverse] = !this[_isReverse];
            return this;
        }

        /**
         * Compares an object or value to another considering the setup of this Comparator
         * @param {*} a - Object or value to compare
         * @param {*} b - Object or value to compare by
         * @returns "-1" for a < b, "0" for a === b or "1" for a > b
         **/
        compare(a, b) {
            return this.compareFnc(a, b);
        }
        
        /**
         * Compares an object or value to another one
         * @param {*} a - Object or value to compare
         * @param {*} b - Object or value to compare by
         * @param {boolean} [missingFirst=false] - order of "undefined" and "null". true = first, false = last.
         * @returns "-1" for a < b, "0" for a === b or "1" for a > b
         **/
        static compare(a, b, missingFirst = false) {
            return compare(a, b, missingFirst);
        }
    }
})();