js策略模式表单

class ValidationStrategy {
  validate(value) {
    throw new Error('validate method must be implemented');
  }
}

class RequiredValidation extends ValidationStrategy {
  validate(value) {
    return value ? true : 'This field is required';
  }
}

class EmailValidation extends ValidationStrategy {
  validate(value) {
    const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
    return emailRegex.test(value) ? true : 'Invalid email format';
  }
}

class MinLengthValidation extends ValidationStrategy {
  constructor(minLength) {
    super();
    this.minLength = minLength;
  }

  validate(value) {
    return value.length >= this.minLength ? true : `Minimum length is ${this.minLength}`;
  }
}

class Validator {
  constructor() {
    this.strategy = null;
  }

  setStrategy(strategy) {
    this.strategy = strategy;
  }

  validate(value) {
    if (!this.strategy) {
      throw new Error('No validation strategy set');
    }
    return this.strategy.validate(value);
  }
}

const validator = new Validator();

// 验证必填字段
validator.setStrategy(new RequiredValidation());
console.log(validator.validate('')); // 输出: This field is required
console.log(validator.validate('some value')); // 输出: true

// 验证邮箱格式
validator.setStrategy(new EmailValidation());
console.log(validator.validate('test@example.com')); // 输出: true
console.log(validator.validate('invalid-email')); // 输出: Invalid email format

// 验证最小长度
validator.setStrategy(new MinLengthValidation(5));
console.log(validator.validate('abc')); // 输出: Minimum length is 5
console.log(validator.validate('abcdef')); // 输出: true