in one of the following forms:

• for array data sources:
  • labelforvalueinarray
  • selectaslabelforvalueinarray
  • labelgroupbygroupforvalueinarray
  • selectaslabelgroupbygroupforvalueinarraytrackbytrackexpr
• for object data sources:
  • labelfor(key,value)inobject
  • selectaslabelfor(key,value)inobject
  • labelgroupbygroupfor(key,value)inobject
  • selectaslabelgroupbygroupfor(key,value)inobject

Where:

• array/object: an expression which evaluates to an array / object to iterate over.
• value: local variable which will refer to each item in thearrayor each property value ofobjectduring iteration.
• key: local variable which will refer to a property name inobjectduring iteration.
• label: The result of this expression will be the label for<option>element. Theexpressionwill most likely refer to thevaluevariable (e.g.value.propertyName).
• select: The result of this expression will be bound to the model of the parent<select>element. If not specified,selectexpression will default tovalue.
• group: The result of this expression will be used to group options using the<optgroup>DOM element.
• trackexpr: Used when working with an array of objects. The result of this expression will be used to identify the objects in the array. Thetrackexprwill most likely refer to thevaluevariable (e.g.value.propertyName).