[toc] ## pre ``` UserSchema.pre('save', function (next) { //第一步先生成鹽值 bcrypt.genSalt((err, salt) => { //通過原始的密碼和鹽值計算哈希值 bcrypt.hash(this.password, salt, (err, hash) => { this.password = hash; next(); }); }); }); ```