JavaScript 上万关键字瞬间匹配——借助Hash表快速匹配算法

来源：

http://www.cnblogs.com/index-html/archive/2013/04/17/js_keyword_match.html

http://www.etherdream.com/funnyscript/Keyword/Keyword.html

适用于多关键字、大文本匹配，若关键字只有一个，则只是最朴素的字符串匹配（逐个匹配），没显示作用。

var treeSearch = {
    makeTree: function(strKeys) {
        "use strict";
        var tblCur = {},
            tblRoot,
            key,
            str_key,
            Length,
            j,
            i
            ;
        tblRoot = tblCur;
        for ( j = strKeys.length - 1; j >= 0; j -= 1) {
            str_key = strKeys[j];
            Length = str_key.length;
            for ( i = 0; i < Length; i += 1) {
                key = str_key.charAt(i);
                if (tblCur.hasOwnProperty(key)) { //生成子节点
                    tblCur = tblCur[key];
                } else {
                    tblCur = tblCur[key] = {};
                }
            }
            tblCur.end = true; //最后一个关键字没有分割符
            tblCur = tblRoot;
        }
        return tblRoot;
    },
    search: function(content, tblRoot) {
        "use strict";
        var tblCur,
            p_star = 0,
            n = content.length,
            p_end,
            match,  //是否找到匹配
            match_key,
            match_str,
            arrMatch = [],  //存储结果
            arrLength = 0   //arrMatch的长度索引
            ;
 
        while (p_star < n) {
            tblCur = tblRoot; //回溯至根部
            p_end = p_star;
            match_str = "";
            match = false;
            do {
                match_key = content.charAt(p_end);
                if (!(tblCur = tblCur[match_key])) { //本次匹配结束
                    p_star += 1;
                    break;
                }else{
                    match_str += match_key;
                }
                p_end += 1;
                if (tblCur.end === true) //是否匹配到尾部  //找到匹配关键字
                {
                    match = true;
                }
            } while (true);
 
            if (match === true) { //最大匹配
                arrMatch[arrLength] = { //增强可读性
                    key: match_str,
                    begin: p_star - 1,
                    end: p_end
                };
                arrLength += 1;
                p_star = p_end;
            }
        }
        return arrMatch;
    }
};

function test(strContent, strKeys) {
    var arrMatch,
        tblRoot = treeSearch.makeTree(strKeys),
        t = new Date();
 
 
    arrMatch = treeSearch.search(strContent, tblRoot);
 
    console.log("time is: " + (new Date() - t) + "mm");
 
    console.log(arrMatch);
}
var s = (function() {
    var Things = [‘ ‘, ‘\n‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘, ‘G‘, ‘H‘, ‘I‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ‘O‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘, ‘a‘, ‘b‘, ‘c‘, ‘d‘, ‘e‘, ‘f‘, ‘g‘, ‘h‘, ‘i‘, ‘j‘, ‘k‘, ‘l‘, ‘m‘, ‘n‘, ‘o‘, ‘q‘, ‘r‘, ‘s‘, ‘t‘, ‘u‘, ‘v‘, ‘w‘, ‘x‘, ‘y‘, ‘z‘];
    var s = "";
    for (var i = 1000000; i >= 0; i--) {
        s += Things[parseInt(Math.random() * Things.length) % Things.length]
    };
    return s;
})()
test(s, ["abc", "efge", "fun", "tree"]);