var userSchema = mongoose.Schema({

    local            : {
        email        : String,
        password     : String,
    }
});

userSchema.methods.validPassword = function(password) {
    user=this;
    return this.local.password; <---------------THIS LINE
};

module.exports = mongoose.model('User', userSchema);

var User = require('./usermodel.js);

    var objectUser = {
    email: "a2@a.com",
    password: "a222"

    };

console.log(objectUser.User.validPassword());

db.find({email: "a2@a.com"}).....