how function that pass to sort method of array access property of object in that array?

Question

function comParison(propertyName){
    return function(obj1,obj2){
       var value1 = obj1[propertyName];
       var value2 = obj2[propertyName];

       if (value1 < value2){
        return -1;
       }else id (value1 > value2){
        return1;
       }else{
        return 0;
       }
    }
  };


var data = [{name:n1},{name:n2}];
data.sort(comParison("name"));

this will compare name, but how does comParison function access name property and why it have to pass as string?

Go checkout associative array in Javascript. That should help. — anuj_io, Jul 07 '13 at 17:11
@tea_totaler What is an _"associative array"_ in _JavaScript_? Do you mean an _Object_ or an _Array_ of _Objects_? — Paul S., Jul 07 '13 at 17:30
*" how does comParison function access name property"* like so: `obj1[propertyName]`. That's called *bracket notation*. *"why it have to pass as string"* because it would not work otherwise. — Felix Kling, Jul 07 '13 at 17:55
Because it's [bracket notation](http://stackoverflow.com/questions/4968406/javascript-property-access-dot-notation-vs-brackets). — Bergi, Jul 07 '13 at 20:18

score 0 · Accepted Answer · edited May 23 '17 at 10:25

Above example is based on closures. Step by step it's roughly like this:

comParison function accepts propertyName as an argument
Anonymous function created inside comParison, that function has access to propertyName and everything else inside comParison (and global variables).
This anonymous function is then returned as a sorting function
By the time this anonymous function is called it still has access to propertyName variable due to closure, and is, therefore, able to access obj[propertyName]

Hope this makes it a bit clear.

Another useful answer.

how function that pass to sort method of array access property of object in that array?

1 Answers1