fastpath.js

function Path(path) {
    this.path = this.parsePathStr(path);
    console.log(this.path);
    this.length = this.path.length;
    /** @override */
    this.get = this.createGetFn();
}

Path.prototype.get = function(obj) {
    for(var i = 0; i < this.length; i++)
        if((obj = obj[this.path[i]]) == null) return;
    return obj;
};

Path.prototype.parsePathStr = function(str) {
    return str.split('.');
};

Path.prototype.createGetFn = function() {
    var key = 'obj',
        fnBody = 'if(' + key;

    for(var i = 0; i < this.length - 1; i++) {
        key += '.' + this.path[i];
        fnBody += ' &&\n' + key + '!=null';
    }

    key += '.' + this.path[i];
    fnBody += ') return ' + key + ';';

    return new Function('obj', fnBody);
};

function test() {
    var obj = {
        a : {
            b : {
                c : [
                    1,
                    { d : [1, 2, 3] },
                    { d : [4, 5] }
                ]
            }
        }
    };
    var path = new Path('a.b.c[1].d');
    var res = path.get(obj);
    console.log(res);
}

test();