arrays - What's the equivalent of type-specific extension methods in JavaScript? -

say have class person. definition following:

function person(name, age) {     this.name = name;     this.age = age; } 

now have array of persons (or people) , want find oldest one. in c#, via extension methods:

person oldest(this ienumerable<person> people) =>     people.orderbydescending(p => p.age).first();  // usage: var elder = people.oldest(); 

what's equivalent in javascript? far, able come with:

array.prototype.oldest = function() {     return this.slice().sort(function(left, right) {         return left.age - right.age;     }).pop(); }; 

this works , has same syntax c#, has few drawbacks:

1) modifies prototype of builtin, potentially lead conflicts other libraries so.

2) not type-safe: it's easy accidentally call on array doesn't contain people, lead runtime error.

alternatively, define this:

function oldest(people) {     // ... } 

but have call oldest(people) instead of people.oldest(), hamper readability.

is there type-safe, syntactically "nice" way in javascript i'm missing?

because js isn't type safe, you're better off implementing method oldest(people) ...

just think of decorator pattern - legit approach projecting functionality unknown set of related entities.

then - can type-checking within function.

you namespace make syntax more "obvious" if that's concern guess:

personlist(persons).getoldest() 

as 1 objective-c-ish example.

then, can add type-specific checking creator personlist:

function personlist(persons) {       //iterate on persons , make sure       //it's valid. return undefined or {} if not.        return {          getoldest: function() {               // insert clever code here ...               persons.slice().dice().puree();           },           getyoungest: function() {              //even more clever code here ...           }       }  } 

with approach, code

personlist(cats).getoldest() 

with throw 'getoldest undefined' error -- makes easy spot problem when have 11,000,000 lines of js code sort through.

it has added advantage of making c# inner-child feel more @ home (with js file called "arrayextensions.persons.js" in project folder). feels "chicken soup c# soul," right?