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JavaScript JavaScript Foundations Objects Prototypes: Part 2

Louis Darby
Louis Darby
5,149 Points

Regarding Prototypes

Hi, I was wondering if it is possible to write a function that essentially searches through all of one category of your prototype object. Say you made lots of new Person objects with your prototype, could you then retrieve all objects with one property. For example, could you write an if statement that said if age = x print name? Essentially searching through the data you've made via new prototype.

2 Answers

Hi, Lous:

Yes, JS allows you to check for a particular property through hasOwnProperty which you can use to do what you seek to accomplish.

Perhaps even better for your case is to set the property's enumerable value to false in order for it to automatically be ignored in any enumerable operation you do throughout your program.

Does this make sense?

Louis Darby
Louis Darby
5,149 Points


Thanks for the help! It does make sense! However, I'm trying to check for a value of the property rather than if an object has a particular property. Is that possible to do this? For example as mentioned before, all objects will share the place_of_birth property but will vary in their values, I want to be able to see which objects have a value of London for their place_of_birth property.

Appreciate the help.

Hello again, Louis Darby:

You can in fact do this after you verified that the object has the property you want to check the value of; you simply add an additional if/else clause or a ternary operator (?) to accomplish this.

I'm not sure if I quite understand, but it sounds certainly do-able. You'd just make an array, populate it with your various Person instances, loop through the array setting x equal to the index and loop through something similar to:

//Assume personsArray has been populated with multiple Person prototypes
 for(int x = 0; x < personsArray.length; x++){
  if(personArray[x].age == 18){  
//Would be better to just set a variable to represent personsArray[x] to follow DRY

Very sloppy code, but just look at it as a basis. I'll review it when I'm not busy.

Louis Darby
Louis Darby
5,149 Points

Thanks for the response. My fault, i'll try and clarify a bit. If you had your prototype set up as was shown (correct me if I'm wrong):

var personPrototype = { 
            name: "anon",
            age: "number",
            place_of_birth: "location",

function Person (name, age, place_of_birth) {
           this.name = name,
           this.age = age,
           this.place_of_birth = location

Person.prototype = personPrototype

and then you made your new objects using the prototype e.g;

Louis.new Person ("Louis",24,"London");
John.new Person ("John",25,"Madrid");
Chris.new Person ("Chris",22, London");

Could you then create a function, such as an if statement that said if the place_of_birth = "London", console.log (name). But would still work no matter how many objects you made through the prototype?

Hope that makes more sense, appreciate the help.