Expression Function¶

What is an expression function?¶

Expression functions are predefined functions that can be called in multiple places within a project. When you execute an expression function, you can pass parameters to it to get the execution result, which helps avoid writing the same logic repeatedly.

Expression functions are located under Project > Function in the editor.

Create Expression Function¶

To create an expression function, right-click on the "Expression Function" node under "Function" and select "Add".

Note：In use, Expression function is referred to by name, so all references to the expression function need to be updated when renaming. Property

Where can expression functions be used?¶

In any property binding interface that supports Expression, you can access expression functions through the ExpressionFunction namespace.

Example: Tank alarm level determination¶

1. Create an expression function named getTankAlarmLevel with the following script

   // @param {number} level - Current level
   // @param {number} maxLevel - Maximum level
   // @returns {number} Alarm level: 0-Normal, 1-Warning, 2-Alarm
   export function getTankAlarmLevel(level: number, maxLevel: number) {
       if (level >= maxLevel * 0.9 || level <= maxLevel * 0.1) {
           return 2; // Alarm
       } else if (level >= maxLevel * 0.8 || level <= maxLevel * 0.2) {
           return 1; // Warning
       }
       return 0; // Normal
   }
   

2. Add a rectangular control to the page, click the bind button of background color, and bind the expression property. The script is as follows:

   const currentLevel = tag('@Default:currentLevel');
   const alarmLevel = ExpressionFunction.getTankAlarmLevel(currentLevel, 10);
   
   if(alarmLevel === 2){
     return "#FF0000";// Red - Alarm
   }
   
   if(alarmLevel === 1){
     return "#FFFF00";// Yellow - Warning
   }
   
   return "#00FF00";//  Green - Normal