理解策略模式

Node.js

1// --- Strategies: each defines `authenticate()` ---
2class PasswordLogin {
3  authenticate({ username, password }) {
4    console.log(`[PasswordLogin] Authenticating ${username}`);
5    return password === "secret";
6  }
7}
8
9class OtpLogin {
10  authenticate({ phone, otp }) {
11    console.log(`[OtpLogin] Verifying ${phone} with code ${otp}`);
12    return otp === 1234;
13  }
14}
15
16class GoogleLogin {
17  authenticate({ token }) {
18    console.log(`[GoogleLogin] Checking Google token: ${token}`);
19    return token.startsWith("valid-");
20  }
21}
22
23// --- Context: delegates to whichever strategy is active ---
24class AuthService {
25  constructor(strategy) {
26    this.strategy = strategy;
27  }
28
29  setStrategy(strategy) {
30    this.strategy = strategy;
31  }
32
33  login(credentials) {
34    if (!this.strategy) throw new Error("No strategy set");
35    const ok = this.strategy.authenticate(credentials);
36    console.log(`Login ${ok ? "successful" : "failed"}\n`);
37    return ok;
38  }
39}
40
41// --- Usage ---
42const auth = new AuthService(new PasswordLogin());
43auth.login({ username: "alice", password: "secret" });
44
45auth.setStrategy(new OtpLogin());
46auth.login({ phone: "+15551234", otp: 1234 });
47
48auth.setStrategy(new GoogleLogin());
49auth.login({ token: "valid-xyz" });

TypeScript

1interface LoginStrategy {
2  authenticate(credentials: any): boolean;
3}
4
5// --- Strategies: each defines `authenticate()` ---
6class PasswordLogin implements LoginStrategy {
7  authenticate({ username, password }: any): boolean {
8    console.log(`[PasswordLogin] Authenticating ${username}`);
9    return password === "secret";
10  }
11}
12
13class OtpLogin implements LoginStrategy {
14  authenticate({ phone, otp }: any): boolean {
15    console.log(`[OtpLogin] Verifying ${phone} with code ${otp}`);
16    return otp === 1234;
17  }
18}
19
20class GoogleLogin implements LoginStrategy {
21  authenticate({ token }: any): boolean {
22    console.log(`[GoogleLogin] Checking Google token: ${token}`);
23    return token.startsWith("valid-");
24  }
25}
26
27// --- Context: delegates to whichever strategy is active ---
28class AuthService {
29  constructor(private strategy: LoginStrategy) {}
30  
31  setStrategy(strategy: LoginStrategy) {
32    this.strategy = strategy;
33  }
34  
35  login(credentials: any): boolean {
36    const ok = this.strategy.authenticate(credentials);
37    console.log(`Login ${ok ? "successful" : "failed"}\n`);
38    return ok;
39  }
40}
41
42// --- Usage ---
43const auth = new AuthService(new PasswordLogin());
44auth.login({ username: "alice", password: "secret" });
45
46auth.setStrategy(new OtpLogin());
47auth.login({ phone: "+15551234", otp: 1234 });
48
49auth.setStrategy(new GoogleLogin());
50auth.login({ token: "valid-xyz" });