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JavaScriptでEnumを定義する

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GASとかちょっとしたJavaScript使う時にいつの間にかちょっとだけEnum使いたい時のメモ

enum.js
/**
 * Enumの実装クラス
 */
Enum = function() {
    this._enums = [];
    this._lookups = {};
};

/**
 * enumを取得する
 * @return {array} enumオブジェクト
 */
Enum.prototype.getEnums = function() {
    return _enums;
};

/**
 * 繰り返し処理する
 * @param {array} callback コールバック
 */
Enum.prototype.forEach = function(callback){
    var length = this._enums.length;
    for (var i = 0; i < length; ++i){
        callback(this._enums[i]);
    }
};

/**
 * enumを追加する
 * @param {object} e enumの追加情報
 */
Enum.prototype.addEnum = function(e) {
    this._enums.push(e);
};

/**
 * 名前を取得する
 * @param {string} name 名前
 * @return {string} 名前文字列
 */
Enum.prototype.getByName = function(name) {
    return this[name];
};

/**
 * 値を取得する
 * @param  {string} field フィールド
 * @param  {object} value 値
 * @return {object} 設定した値
 */
Enum.prototype.getByValue = function(field, value) {
    var lookup = this._lookups[field];
    if(lookup) {
        return lookup[value];
    } else {
        this._lookups[field] = ( lookup = {});
        var k = this._enums.length - 1;
        for(; k >= 0; --k) {
            var m = this._enums[k];
            var j = m[field];
            lookup[j] = m;
            if(j == value) {
                return m;
            }
        }
    }
    return null;
};

/**
 * Enumを定義する
 * @param  {object} definition 定義内容
 * @return {object} enum
 */
function defineEnum(definition) {
    var k;
    var e = new Enum();
    for(k in definition) {
        var j = definition[k];
        e[k] = j;
        e.addEnum(j);
    }
    return e;
}

使い方

main.js
// 定義
var COLORS = defineEnum({
    RED : {
        value : 1,
        string : 'red'
    },
    GREEN : {
        value : 2,
        string : 'green'
    },
    BLUE : {
        value : 3,
        string : 'blue'
    }
});

// 文字列を取得
COLORS.BLUE.string;
// 値を取得
COLORS.BLUE.value;
// 名前を元に文字列を取得
COLORS.getByName('BLUE').string;
// 値を元に文字列を取得
COLORS.getByValue('value', 1).string;
// enumの定義されている値一覧を処理する
COLORS.forEach(function(e){

});

参考URL

https://code.i-harness.com/ja/q/4649f

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