JS 实现 HashMap

HashMap代码(这种实现方式是错误的，错误原因：代码中_map、_length变量是HashMap的所有实例共用的)：

/**
 * HashMap
 * 2021年09月09日
 */

(function (global) {
    var _map;
    var _length;

    global.HashMap = function () {
        _map = {};
        _length = 0;
    };

    global.HashMap.prototype = {
        put: function (key, value) {
            if (!_map.hasOwnProperty(key)) {
                _length++;
            }
            _map[key] = value;
        },

        get: function (key) {
            if (_map.hasOwnProperty(key)) {
                return _map[key];
            }
            return null;
        },

        containsKey: function (key) {
            return _map.hasOwnProperty(key);
        },

        size: function () {
            return _length;
        },

        remove: function (key) {
            if (_map.hasOwnProperty(key)) {
                _length--;
                return delete _map[key];
            }
            return false;
        },

        removeAll: function () {
            _map = {};
        },

        keys: function () {
            var keys = [];
            for (var item in _map) {
                keys.push(item);
            }
            return keys;
        },

        values: function () {
            var values = [];
            for (var item in _map) {
                values.push(_map[item]);
            }
            return values;
        }
    };

    global.HashMap.prototype.constructor = global.HashMap;

})(window);

View Code

HashMap代码(正确的实现)：

/**
 * HashMap
 * 2021年09月09日
 */

HashMap = function () {
    this._length = 0;
    this._map = {};
};

HashMap.prototype = {
    put: function (key, value) {
        if (!this._map.hasOwnProperty(key)) {
            this._length++;
        }
        this._map[key] = value;
    },

    get: function (key) {
        if (this._map.hasOwnProperty(key)) {
            return this._map[key];
        }
        return null;
    },

    containsKey: function (key) {
        return this._map.hasOwnProperty(key);
    },

    size: function () {
        return this._length;
    },

    remove: function (key) {
        if (this._map.hasOwnProperty(key)) {
            this._length--;
            return delete this._map[key];
        }
        return false;
    },

    removeAll: function () {
        this._length = 0;
        this._map = {};
    },

    keys: function () {
        var keys = [];
        for (var item in this._map) {
            keys.push(item);
        }
        return keys;
    },

    values: function () {
        var values = [];
        for (var item in this._map) {
            values.push(this._map[item]);
        }
        return values;
    }
};

HashMap.prototype.constructor = HashMap;

View Code

测试代码：

<!DOCTYPE html>
<html>
<head>
    <title>HashMap测试</title>

    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <style type="text/css">
    </style>

    <script type="text/javascript" src="jquery-1.7.1.js"></script>
    <script type="text/javascript" src="hashmap.js"></script>

</head>
<body>
    <input type="button" value="测试1" onclick="testHashMap()" />
    <input type="button" value="测试2" onclick="testArray()" />
    <div id="div" style="height:800px;"></div>

    <script type="text/javascript">
        var n = 100000;
        var div = $("#div");

        //测试数据
        debugger;
        var list = [];
        var map = new HashMap();
        for (var i = 1; i <= n; i++) {
            var val = Math.floor(Math.random() * n);
            var key = "key" + val;

            if (!map.containsKey(key)) {
                map.put(key, val);
                list.push({ key: key, value: val });
            }
        }
        div.append("测试数据初始化完成，数据量：Array " + list.length + "，HashMap " + map.size() + "<br />");

        //测试HashMap
        function testHashMap() {
            var t1 = new Date().getTime();

            var sum = 0;
            var count = 0;
            for (var i = 20000; i <= 21000; i++) {
                var key = "key" + i;

                if (map.containsKey(key)) {
                    var num = map.get(key);
                    count++;
                    sum += num;
                }
            }

            var t2 = new Date().getTime();

            div.append("完成，结果：sum=" + sum + "，count=" + count + "耗时" + (t2 - t1).toString() + "毫秒<br />");
        }

        //测试Array
        function testArray() {
            var t1 = new Date().getTime();

            var sum = 0;
            var count = 0;
            for (var i = 20000; i <= 21000; i++) {
                for (var k = 0; k < list.length; k++) {
                    var key = "key" + i;
                    var item = list[k];

                    if (item.key == key) {
                        count++;
                        sum += item.value;
                    }
                }
            }

            var t2 = new Date().getTime();

            div.append("完成，结果：sum=" + sum + "，count=" + count + "耗时" + (t2 - t1).toString() + "毫秒<br />");
        }

    </script>
</body>
</html>

View Code

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原文地址：https://www.cnblogs.com/s0611163/p/15246905.html