Scripting allows you to change the properties of visual elements at run time, to create animations, to react, to user input in complex ways, and even interact with external servers by sending and receiving data. See Data, State Transitions, Visual Elements. The result is a dynamic user interface and other functionality that UJML cannot otherwise provide.

There are two different methods of adding scripting statements to UJML: XML scripting elements and the script block scripting language. See XML Scripts, Script Blocks. These provide similar capabilities, although the scripting language is the preferred scripting method. Both work with UJML in a manner similar to how JavaScript works with HTML. 

Note: XML scripting and the scripting language may be mixed in the same UJML program. Although this is not encouraged, UJML will allow it.

Both scripting methods allow you to add procedural, or one-step-at-a-time, code to the declarative elements of UJML. These procedural scripting statements are executed when the state transition, function, or other UJML element that contains them is executed. When this happens, the scripting statements are executed in they order they occur in the UJML code until all scripting code inside that UJML element is completed. See Execution Order.

Besides procedural scripting, both forms of UJML scripting allow runtime-evaluated expressions which return a value. See Script Expressions. This may be a function call, a mathematical calculation or a Boolean comparison—any single scripting statement that yields a value. For example, you might use an expression to calculate visual element property values, such as location and color, when the visual element is displayed.

Within both procedural and expression scripting statements you may also call functions. See Using Functions, Functions. You may also use scripting to create your own functions. See User Defined Functions.

Execution Order, Data, State Transitions, Visual Elements, User Defined Functions, Functions