策略模式

strategy.js

/* Title: Strategy

Description: allows one of a family of algorithms to be selected on-the-fly at runtime

*/
// 用法
var data = {
  first_name: "Super",
  last_name: "Man",
  age: "unknown",
  username: "o_O"
};

validator.config = {
  first_name: 'isNonEmpty',
  age: 'isNumber',
  username: 'isAlphaNum'
};

validator.validate(data);

if (validator.hasErrors()) {
  console.log(validator.messages.join("\n"));
}


// 實作
var validator = {
  // all available checks
  types: {},
  
  // error messages in the current
  // validation session
  messages: [],
  
  // current validation config
  // name: validation type
  config: {},
  
  // the interface method
  // 'data' is key => value pairs
  validate: function(data) {
    var i, msg, type, checker, result_ok;
    
    // reset all messages
    this.messages = [];
    
    for (i in data) {
      if (data.hasOwnProperty(i)) {
        type = this.config[i];
        checker = this.types[type];
        
        if (!type) {
          continue; // no need to validate
        }
        if (!checker) { // uh-oh
          throw {
            name: "ValidationError",
            message: "No handler to validate type " + type
          };
        }
        
        result_ok = checker.validate(data[i]);
        if (!result_ok) {
          msg = "Invalid value for *" + i + "*, " + checker.instructions;
          this.messages.push(msg);
        }
      }
    }
    return this.hasErrors();
  },
  
  // helper
  hasErrors: function() {
    return this.messages.length !== 0;
  }
};

// checks for non-empty values
validator.types.isNonEmpty = {
  validate: function(value) {
    return value !== "";
  },
  instructions: "the value cannot be empty"
};

// checks if a value is a number
validator.types.isNumber = {
  validate: function(value) {
    return !isNaN(value) && value / Infinity === 0;
  },
  instructions: "the value can only be a valid number, e.g. 1, 3.14 or 2010"
};

// checks if the value contains only letters and numbers
validator.types.isAlphaNum = {
  validate: function(value) {
    return !/[^a-z0-9]/i.test(value);
  },
  instructions: "the value can only contain characters and numbers, no special symbols"
};