MongoDB & Mongoose

1// MongoDB with Mongoose — Complete Setup
2
3const mongoose = require("mongoose");
4
5// 1. Connection with best practices
6async function connectDB() {
7  try {
8    await mongoose.connect(process.env.MONGODB_URI || "mongodb://localhost:27017/myapp", {
9      maxPoolSize: 10,
10      serverSelectionTimeoutMS: 5000,
11      socketTimeoutMS: 45000,
12    });
13    console.log("MongoDB connected");
14  } catch (err) {
15    console.error("MongoDB connection error:", err);
16    process.exit(1);
17  }
18}
19
20// Connection events
21mongoose.connection.on("error", (err) => console.error("MongoDB error:", err));
22mongoose.connection.on("disconnected", () => console.log("MongoDB disconnected"));
23
24// 2. Schema definition with validation
25const userSchema = new mongoose.Schema(
26  {
27    name: {
28      type: String,
29      required: [true, "Name is required"],
30      trim: true,
31      minlength: [2, "Name must be at least 2 characters"],
32      maxlength: [50, "Name cannot exceed 50 characters"],
33    },
34    email: {
35      type: String,
36      required: [true, "Email is required"],
37      unique: true,
38      lowercase: true,
39      trim: true,
40      match: [/^[^\s@]+@[^\s@]+\.[^\s@]+$/, "Invalid email format"],
41    },
42    password: {
43      type: String,
44      required: true,
45      minlength: 8,
46      select: false, // Don't include in queries by default
47    },
48    role: {
49      type: String,
50      enum: ["user", "admin", "moderator"],
51      default: "user",
52    },
53    profile: {
54      bio: { type: String, maxlength: 500 },
55      avatar: String,
56      social: {
57        twitter: String,
58        github: String,
59      },
60    },
61    posts: [{ type: mongoose.Schema.Types.ObjectId, ref: "Post" }],
62    isActive: { type: Boolean, default: true },
63    loginCount: { type: Number, default: 0 },
64    lastLogin: Date,
65  },
66  {
67    timestamps: true, // Adds createdAt and updatedAt
68    toJSON: { virtuals: true },
69    toObject: { virtuals: true },
70  }
71);
72
73// 3. Virtual fields (computed, not stored in DB)
74userSchema.virtual("displayName").get(function () {
75  return this.name.charAt(0).toUpperCase() + this.name.slice(1);
76});
77
78// 4. Instance methods
79userSchema.methods.comparePassword = async function (candidatePassword) {
80  const bcrypt = require("bcryptjs");
81  return bcrypt.compare(candidatePassword, this.password);
82};
83
84// 5. Static methods (on the Model)
85userSchema.statics.findByEmail = function (email) {
86  return this.findOne({ email: email.toLowerCase() });
87};
88
89userSchema.statics.findActiveUsers = function () {
90  return this.find({ isActive: true }).sort("-createdAt");
91};
92
93// 6. Middleware (hooks)
94userSchema.pre("save", async function (next) {
95  // Hash password before saving
96  if (this.isModified("password")) {
97    const bcrypt = require("bcryptjs");
98    this.password = await bcrypt.hash(this.password, 12);
99  }
100  next();
101});
102
103// 7. Indexes
104userSchema.index({ email: 1 }, { unique: true });
105userSchema.index({ name: "text", "profile.bio": "text" }); // Text search
106userSchema.index({ createdAt: -1 }); // Sort optimization
107
108// 8. Create model
109const User = mongoose.model("User", userSchema);
110
111// 9. CRUD Operations
112async function userCrudExamples() {
113  // CREATE
114  const user = await User.create({
115    name: "Alice",
116    email: "alice@example.com",
117    password: "securepass123",
118  });
119
120  // READ
121  const allUsers = await User.find({ isActive: true })
122    .select("name email role")
123    .sort("-createdAt")
124    .limit(10)
125    .lean(); // Returns plain objects (faster)
126
127  const singleUser = await User.findById(user._id);
128  const byEmail = await User.findByEmail("alice@example.com");
129
130  // UPDATE
131  await User.findByIdAndUpdate(
132    user._id,
133    { $set: { role: "admin" }, $inc: { loginCount: 1 } },
134    { new: true, runValidators: true }
135  );
136
137  // DELETE
138  await User.findByIdAndDelete(user._id);
139
140  // Aggregation
141  const stats = await User.aggregate([
142    { $match: { isActive: true } },
143    { $group: { _id: "$role", count: { $sum: 1 }, avgLogins: { $avg: "$loginCount" } } },
144    { $sort: { count: -1 } },
145  ]);
146
147  // Population (join-like)
148  const userWithPosts = await User.findById(user._id).populate("posts");
149}
150
151module.exports = { User, connectDB };