Search code examples
javascriptenumerated-types

Example: Enumerated Types ("JavaScript, O'Reilly Publishing")

Has anyone read "JavaScript, The Definitive Guide" (O'Reilly)?

I spent several hours digesting Example 9-7.

In particular, the .foreach() "class" method has me somewhat puzzled.

Also, does .valueOf get called automatically?

Thank you in advance.

Solution

  • Also, does .valueOf get called automatically?

    valueOf and toString are called "automatically". valueOf if the object i question is converted to a number, and toString, well, if it is converted to a string.

    function Foo(){}

Foo.prototype = {
  constructor: Foo,
  valueOf: function() { return 2; },
  toString: function () { return 'bar' }
}

var f = new Foo();
f + f + 2 //6
'' + f   //"bar"

    But if you would have read the book, you should know that already.

    In particular, the .foreach() "class" method has me somewhat puzzled.

    Why? It is a member of Array.prototype, well documented and extremly handy. Or do you refering to another example?