Mongoose SchemaTypes Getters

Mongoose 是在 Node.js 和 MongoDB 中 MongoDB 的一种流行的对象数据建模（ODM）库. Mongoose 可以使用 SchemaTypes 为模式字段定义自定义的获取器和设置器。 获取器 允许您定义一个函数，该函数在从数据库返回模式字段的原始值之前将其转换。这对于在 MongoDB 中格式化、解析或加密存储的数据非常有用。

参数: 为 SchemaType 定义的获取器函数应该接受一个参数和要转换的字段的值。该函数可以返回任何应该用作字段的转换值的值。如果函数返回 undefined，则将使用字段的原始值。

语法:

const mySchema = new mongoose.Schema({
    field: {
        type: String,
        get: function(value) {
            // Transform and return value here
            return transformedValue;
        }
    }
});

示例1： 在这里，我们使用javascript内置函数toUpperCase。当用户输入任何小写或大写字母时，在其传递到MongoDB之前，它会自动转换为大写字母。

// Import the mongoose 
const mongoose = require('mongoose'); 
  
// User Schema 
// Define the schema for the "Geek" object 
const geekSchema = new mongoose.Schema({ 
    name: { 
  
        // The "name" field is of type "String" 
        type: String, 
          
        // A getter function that returns the  
        // value of the "name" field in uppercase 
        get: (name) => name.toUpperCase() 
    } 
}); 
  
// User model 
// Create a model for the "Geek" object 
// using the "geekSchema" schema 
const Geek = mongoose.model('Geek', geekSchema); 
  
// Create a new "Geek" object with the "name"  
// field set to "geeksforgeeks" 
const geek = new Geek({ name: 'geeksforgeeks' }); 
  
// Log the value of the "name" field on the console 
console.log(geek.name); // Output: "GEEKSFORGEEKS" 

输出：

示例2： 在这里，我们制作了一个包含邮件和密码的模式，其中我们尝试隐藏邮件并加密密码。为了隐藏邮件，我们将建立自己的函数，并使用md5散列。首先，我们必须在应用程序中使用命令提示符中的命令安装md5。

npm i md5

// Import required dependencies 
// Import Mongoose for defining the  
// schema and model 
const mongoose = require('mongoose'); 
  
// Import MD5 for encrypting the password 
const md5 = require('md5'); 
  
// Define the user schema 
const userSchema = new mongoose.Schema({ 
    email: { 
  
        // Set the data type to string 
        type: String, 
          
        // Define a getter function for email field 
        get: (email) => { 
  
            // Initialize a variable for storing 
            // the masked email 
            let masked = ""; 
  
            // Get the actual email value 
            let mailId = email; 
              
            // Get the prefix part of email 
            let prefix = mailId.substring(0,  
                mailId.lastIndexOf("@")); 
              
            // Get the postfix part of email 
            let postfix = mailId.substring( 
                mailId.lastIndexOf("@")); 
  
            // Loop through each character of prefix 
            for (let i = 0; i < prefix.length; i++) { 
  
                // Keep first and last characters unmasked 
                if (i == 0 || i == prefix.length - 1) { 
  
                    // Append the unmasked character 
                    // to masked string  
                    masked = masked + prefix[i].toString(); 
                } 
                else { 
                    // Mask all other characters with '*' 
                    masked = masked + "*"; 
                } 
            } 
  
            // Add the postfix to masked string 
            masked = masked + postfix; 
            return masked; // Return the masked email 
        } 
    }, 
    password: { 
  
        // Set the data type to string 
        type: String, 
  
        // Define a getter function for password  
        // field to encrypt the value using MD5 
        get: (type) => md5(type) 
    } 
}); 
  
// Create a user model from the schema 
const User = mongoose.model('User', userSchema); 
  
// Create a new user instance with email and password 
const user = new User({  
    email: 'abc1452@gmail.com',  
    password: '1234' 
}); 
  
// Log the masked email and encrypted 
// password of the user 
  
// Output: a******@gmail.com 
console.log(user.email); 
  
// Output: 81dc9bdb52d04dc20036dbd8313ed055 
console.log(user.password); 

输出：