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 This article describes a feature or macro function that is experimental and may be subject to change.

js.eval() Function

 Note: This function can only be used in a Trusted Macro

Introduced in version 1.10.0
Evaluates a string as a javascript expression. Supports ECMA 2021 standard. For security, access to native types and external resources are limited. Similarly, all arrays passed in to the javascript environment are shallow copied, so changes to the array do not directly change MapTool's state. Starting in 1.10.0, the context in which the javascript fragment executes is discarded when
returns. For setting up persistent structures, see js.evalNS() or js.evalURI()


js.eval(expression, arg1, arg2...)


  • expression - A valid javascript fragment. It is wrapped inside an anonymous function.
  • arg1, arg2... - Any. Will be converted to the equivalent javascript type as needed. Arguments are accessible via the args variable.
  • return - Any primitive type; Complex types are converted to (JSON) strings.


Using js.eval on an expression.
[r: js.eval("let a = [1,2,3]; return a[1] + args[0]", 5)]



See Also