define

redefines a single configuration property (or a object with properties)

void define(string| object property, [any value] );

property	string\| object	the property name or a object with properties that need redefining
value	any	the new property value (has to be specified when defining the property as a string)

// redefines the width of the list
$$("diagram1").define("width", 500);
$$("diagram1").refresh();

Details

The component should be refreshed to reflect the changes.

You can also use the config property to change the desired configuration option:

$$("myList").config.width = 300:
$$("myList").resize();