JavaScript上万关键字瞬间匹配

• ， 3 3月 2019
• 作者 hliang
• TypeScript/JavaScript

JavaScript上万关键字瞬间匹配

既然考虑的是那种极端的关键字搜索，通常的逐个遍历搜索显然是行不通的。如今用的是JavaScript，若不使用Hash表实在是太对不起这门语言了。有着对表特天独厚的支持，不妨就拿出少量的空间来换取大量的时间吧。

代码在下面：

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;
    }
};

测试代码：

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']);