The new Uize.isList static method returns a boolean, indicating whether or not the specified value is considered a list.

SYNTAX

isListBOOL = Uize.isList (valueANYTYPE);

A list is considered to be a non-null value of type 'object' that has a length property whose value is a number. By this definition, an instance of JavaScript's built-in Array object is considered to be a list. Also by this definition, a NodeList instance as returned by the document.getElementsByTagName method is considered to be a list, since it is a non-null object type value with a number type length property.

The Uize.isList method is useful when implementing methods that are to conditionalize their behavior based upon the type of a parameter, and where an iteration behavior is desired for list type values. If a value is considered to be a list, its list items can be iterated over using a standard JavaScript for loop, using the length property to determine how many items should be iterated over, and indexing into the list using JavaScript's [] (square brackets) notation.

EXAMPLES

alert (Uize.isList (['foo','bar','hello','world']));        // alerts "true"
alert (Uize.isList (document.getElementsByTagName ('a')));  // alerts "true"

alert (Uize.isList ({foo:'bar',hello:'world'}));            // alerts "false"
alert (Uize.isList (42));                                   // alerts "false"
alert (Uize.isList (true));                                 // alerts "false"
alert (Uize.isList ('foo');                                 // alerts "false"
alert (Uize.isList (null);                                  // alerts "false"
alert (Uize.isList (undefined);                             // alerts "false"
alert (Uize.isList (/\d+/));                                // alerts "false"
alert (function () {});                                     // alerts "false"

// an object is only considered a list once it has a length property that is a number
var fooObj = {0:'foo',1:'bar',2:'hello',3:'world'};
alert (Uize.isList (fooObj));                               // alerts "false"
fooObj.length = '4';
alert (Uize.isList (fooObj));                               // alerts "false"
fooObj.length = 4;
alert (Uize.isList (fooObj));                               // alerts "true"

// the arguments variable inside functions is considered to be a list
function fooFunc () {
  alert (Uize.isList (arguments));                         // alerts "true"
}
fooFunc ('foo','bar','hello','world');

This new method is thoroughly documented and has comprehensive unit tests.