node.js Array.length issue

Question

array.length is returning 0 always.... Its returning 0 even some item added into the array...

 function validate () { 

  error = new Array();

  if(req.body.category_id==""){ 
    error['category_id'] = "Please select category";
  }

  if(req.body.text==""){ 
    error['text'] = "Enter the word";
  }

  if(!(req.body.email!="" && req.body.email.test(/@/))){ 
    error['email'] = "Invalid email id";
  }

  if((req.session.number1+req.session.number2)!=req.body.captcha){ 
    error['captcha'] = "Captcha verification failed";
  }  

 console.log(error.length);
 console.log(error['category_id']);

  if(error.length){ 
    return false;   
  }else{ 
    return true;
  }
}

result of the console.log
//0
//Please select category

Answer 1

Array.length only counts values whose key is numeric . You are using strings as the keys, so your length is always 0. Though legal, (since Arrays are Objects) this is confusing and isn't a good fit for an array.

As @Sudhir suggests, use an "object" or "hash" : the { } notation. Much clearer. (Though I disagree with him modifying with the Object.prototype)

Answer 2

Javascript does not have associative arrays, make it object like:

//function to get size of object
Object.prototype.size = function(obj) {
    var size = 0, key;
    for (key in obj) {
        if (obj.hasOwnProperty(key)) size++;
    }
    return size;
};
var error = {}; //object
if(req.body.category_id==""){ 
    error['category_id'] = "Please select category";
}
...
//rest of your code
if( Object.size(error) ){ //check if we have error
    return false;   
}else{ 
    return true;
}

//check the size of object
console.log(  Object.size(error) );
console.log(error['category_id']);

Answer 3

var error = function(){};
error.prototype.test=[1,2,3];  //1,2,3 only example
console.log(new error().test.length);

Use JavaScript.prototype

But objects created with this function will have this property in their prototype chain (as prototype property of error points to the object that has test property defined.