javascript设计模式之解释器模式详解(8/23)

本篇文章主要介绍了"javascript设计模式之解释器模式详解"，主要涉及到javascript设计模式方面的内容，对于Javascriptjrs看球网直播吧_低调看直播体育app软件下载_低调看体育直播感兴趣的同学可以参考一下： 神马是“解释器模式”？先翻开《GOF》看看Definition：给定一个语言，定义它的文法的一种表示，并定义一个解释器，这个解释器使用该表示来解释语言中的句子。...

        Context.prototype = {
            // 重新初始化上下文
            reInit: function () {
                this.preEles = [];
            },
            /**
             *  各个Expression公共使用的方法
             * 根据父元素和当前元素的名称来获取当前元素
             * @param  {Element} pEle    [父元素]
             * @param  {String} eleName [当前元素名称]
             * @return {Element|null}         [找到的当前元素]
             */
            getNowEles: function (pEle, eleName) {
                var elements = [];
                var tempNodeList = pEle.childNodes;
                var nowEle;

                for (var i = 0, len = tempNodeList.length; i < len; i++) {
                    if ((nowEle = tempNodeList[i]).nodeType === 1) {
                        if (nowEle.nodeName === eleName) {
                            elements.push(nowEle);
                        }
                    }
                }

                return elements;
            },
            getPreEles: function () {
                return this.preEles;
            },
            setPreEles: function (nowEles) {
                this.preEles = nowEles;
            },
            getDocument: function () {
                return this.document;
            }
        };

        // 工具对象
        // 解析xml，获取相应的Document对象
        var XmlUtil = {
            getRoot: function (filePathName) {
                var parser = new DOMParser();
                var xmldom = parser.parseFromString('12345d1d2d3d4', 'text/xml');

                return xmldom;
            }
        };

        /**
         * 元素作为非终结符对应的解释器，解释并执行中间元素
         * @param {String} eleName [元素的名称]
         */
        function ElementExpression(eleName) {
            this.eles = [];
            this.eleName = eleName;
        }

        ElementExpression.prototype = {
            addEle: function (eleName) {
                this.eles.push(eleName);
                return true;
            },
            removeEle: function (ele) {
                for (var i = 0, len = this.eles.length; i < len; i++) {
                    if (ele === this.eles[i]) {
                        this.eles.splice(i--, 1);
                    }
                }
                return true;
            },
            interpret: function (context) {
                // 先取出上下文中的当前元素作为父级元素
                // 查找到当前元素名称所对应的xml元素，并设置回到上下文中
                var pEles = context.getPreEles();
                var ele = null;
                var nowEles = [];

                if (!pEles.length) {
                    // 说明现在获取的是根元素
                    ele = context.getDocument().documentElement;
                    pEles.push(ele);
                    context.setPreEles(pEles);
                } else {
                    var tempEle;
                    for (var i = 0, len = pEles.length; i < len; i++) {
                        tempEle = pEles[i];
                        nowEles = nowEles.concat(context.getNowEles(tempEle, this.eleName));

                        // 找到一个就停止
                        if (nowEles.length) break;
                    }

                    context.setPreEles([nowEles[0]]);
                }

                var ss;
                // 循环调用子元素的interpret方法
                for (var i = 0, len = this.eles.length; i < len; i++) {
                    ss = this.eles[i].interpret(context);
                }