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Expressions

Expressions handler interface.

  • Expressions
    • resolveExpression(expression[, context, fnContext]): resolve expression
    • isExpression(testString): optional function to evaluate if string is an expression
    • hasExpression(testString): optional function to evaluate if the string contains an expression

Standard

resolveExpression(expression[, context, fnContext])

Resolve expression.

Arguments:

  • expression: expresion templated string
  • context: optional context from where to resolve expressions
  • fnContext: optional call context (this)

isExpression(testString)

Evaluate if a string is an expression, and only an expression, e.g. ${environment.variables.supersecret}.

hasExpression(testString)

Evaluate if a string contains an expression, e.g. ${environment.variables.username}:${environment.variables.supersecret}.

Default expression handling

Default expressions come in the form of ${<variables or services>.<property name>}.

The following expressions are supported:

  • ${environment.variables.input} - resolves to the variable input

  • ${environment.variables.input[0]} - resolves to first item of the variable input array

  • ${environment.variables.input[-1]} - resolves to last item of the variable input array

  • ${environment.variables.input[spaced name]} - resolves to the variable input object property spaced name

  • ${environment.services.getInput} - resolves to the service function getInput itself (it is not called). The caller decides how to invoke it — e.g. a sequence flow condition calls it with the flow execution scope

  • ${environment.services.getInput()} - calls the service function getInput. Empty parentheses are not a no-argument call: the resolution context is passed as the single argument, i.e. { environment, ...message } (so the service can read arg.content, arg.environment, …)

  • ${environment.services.isBelow(content.input,2)} - calls the service function isBelow with the resolved content.input value and 2

  • I, ${content.id}, execute with id ${content.executionId} - formats a string addressing content object values

and, as utility:

  • ${true} - return Boolean value true
  • ${false} - return Boolean value false

Expressions in expressions is not supported and has unforeseeable outcome!

Community

expression-parser

A far more advanced expression parser by Aircall.

npm i @aircall/expression-parser