CODEWITHSUNDEEP
javascriptobject
John Abraham
John Abraham

Reputation: 18811

calculate the value of an obj key while using different key/values of the same object?

How can I calculate pageSize.offset from the keyspageSizes.w/pageSize.h inside the same object?

   var pageSizes = {
              w: parseInt(scope.page.imagewidth),
              h: parseInt(scope.page.imageheight),
              offset: (pageSize.w/pageSize.h)
            }

   console.log('page.offset', pageSizes.offset);

currently i'm getting a RefferenceError: pageSize is not defined.

I'm assuming this isn't possible. therefore, what would be the best way to do this?

Upvotes: 0

Views: 43

Answers (3)

dandavis
dandavis

Reputation: 16726

apparently this works in firefox, opera, safari, chrome, and even IE9:

var pageSizes ={
          w: parseInt(scope.page.imagewidth, 10), //Dont forget the radix!
          h: parseInt(scope.page.imageheight, 10), //Dont forget the radix!
           get offset () {
              return this.w/this.h;
          }
 };

it's like the method one, but you don't have to call it, keeping it acting like the other properties.

console-friendly version:

    var pageSizes ={
              w: 5,
              h: 10,
               get offset () {
                  return this.w/this.h;
              }
     };

JSON.stringify(pageSizes); // == "{"w":5,"h":10,"offset":0.5}"

i'd always used Object.defineProperty (ODP) for getters and setters, but this seems to be a lot more supported than i thought. you learn something every day. it looks like a typo, what with the missing colon and "function" and all, but it works. very cool.

thank's to robG for his comment, which made me check the ref again.

see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/get#Example:_Defining_a_getter_with_the_get_operator for details

Upvotes: 3

A.B
A.B

Reputation: 20445

Function has refence to special keyword "this" that points to Current Scope(or protypical scope of parent till global scope) or current Object Instance , Here Points to PageSizes Object Use this

      var pageSizes = {
      w: parseInt(scope.page.imagewidth),
      h: parseInt(scope.page.imageheight),
      offset: function() {
          return this.w/this.h;
      }
    }

and then chnage this line , as offset it not an property it is a function now

    console.log('page.offset', pageSizes.offset);

to

   console.log('page.offset', pageSizes.offset());

Upvotes: 0

tymeJV
tymeJV

Reputation: 104785

Make it a function and use this

var pageSizes = {
          w: parseInt(scope.page.imagewidth, 10), //Dont forget the radix!
          h: parseInt(scope.page.imageheight, 10), //Dont forget the radix!
          offset: function() {
              return this.w/this.h;
          }
        }

console.log('page.offset', pageSizes.offset());

Also, dont forget your radix in the parseInt function

Upvotes: 3

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