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Elsa 2.13

Expressions

JavaScript Expressions

The following JavaScript expressions are supported:

Variables

Workflow Variables

To access a workflow variable, use the getVariable function.

For example, if the SetVariable activity sets a variable called FirstName to 'Luke', it can be accessed as follows:

const firstName = getVariable('FirstName');
 `Hello ${firstName}`

To set a workflow variable, use the setVariable function.

Activity Output (Elsa 2.0)

Any activity might provide some output, which is accessible from any other activity using workflow expressions. To access an activity's output using a JavaScript expression, you can do so by specifying the activity name followed by .Output.

For example, if you have an activity named MyActivity, you can access its output as follows: MyActivity.Output.

If the output is an object, you can access its properties too. For instance, the HTTP Endpoint activity returns the HTTP request as its output which is of type HttpRequestModel. When you name this activity "MyHttpEndpoint", you can access the HTTP request body like this:

MyHttpEndpoint.Output.Body

If you happened to post a JSON document to your HTTP endpoint that looks like this:

{
  "SomeDocument": {
    "Title": "About Elsa Workflows"
  }
}

Then you can access the "Title" field like this:

MyHttpEndpoint.Output.Body.SomeDocument.Title

If your activity is a direct child of an HTTP Endpoint activity, you can access its output directly via the input variable, which will be an instance of HttpRequestModel.

Activity Output (Elsa 2.1)

Any activity might provide some output, which is accessible from any other activity using workflow expressions. To access an activity's output property called e.g. Output using a JavaScript expression, you can do so by specifying activities, then the activity name followed by .Output(). Notice that you must invoke the property as if it were a method. This is due to the way workflow storage providers work, which are potentially asynchronous in nature (such as Azure Blob Storage).

For example, if you have an activity named MyActivity, you can access its output as follows: activities.MyActivity.Output().

If the output is an object, you can access its properties too. For instance, the HTTP Endpoint activity returns the HTTP request as its output which is of type HttpRequestModel. When you name this activity "MyHttpEndpoint", you can access the HTTP request body like this:

activities.MyHttpEndpoint.Output().Body

If you happened to post a JSON document to your HTTP endpoint that looks like this:

{
  "SomeDocument": {
    "Title": "About Elsa Workflows"
  }
}

Then you can access the "Title" field like this:

activities.MyHttpEndpoint.Output().Body.SomeDocument.Title

If your activity is a direct child of an HTTP Endpoint activity, you can access its output directly via the input variable, which will be an instance of HttpRequestModel.

SendHttpRequest Activity

The SendHttpRequest activity has two output properties:

        [ActivityOutput] public HttpResponseModel? Response { get; set; }
        [ActivityOutput] public object? ResponseContent { get; set;

To access a SendHttpRequest activity with name SampleRequest1's response content, use activities.SampleRequest1.ResponseContent().

input

Contains the input value that was received as output from the previously executed activity, if any.

input: object?

workflowInstanceId

Contains the workflow instance ID of the currently executing workflow.

workflowInstanceId: string

workflowDefinitionId

Contains the workflow definition ID of the currently executing workflow.

workflowDefinitionId: string

workflowDefinitionVersion

Contains the workflow definition version of the currently executing workflow.

workflowDefinitionVersion: number

correlationId

Contains the correlation ID of the currently executing workflow.

correlationId: string?

currentCulture

Contains the current culture.

currentCulture: CultureInfo

Currently, this value is always set to CultureInfo.InvariantCulture.

workflowContext

Contains the workflow context (if any) of the currently executing workflow.

workflowContext: object?

currentCulture

Returns the current culture.

currentCulture: CultureInfo

Common Functions

guid

Generates a new GUID value and returns its string representation.

guid(): string

This function is a thin wrapper around the following .NET code: Guid.NewGuid().ToString().

parseGuid

Parses a string into a GUID value.

parseGuid(value: string): Guid

This function is a thin wrapper around the following .NET code: Guid.Parse(value).

setVariable

Sets a workflow variable to the specified value.

setVariable(name: string, value: object): void

This function is a thin wrapper around the following .NET code: activityContext.SetVariable(name, value).

getVariable

Returns a workflow variable with the specified name.

getVariable(name: string): object

Instead of using getVariable(name: string), you can access workflow variables directly as described above in the Workflow Variables section.

This function is a thin wrapper around the following .NET code: activityContext.GetVariable(name).

getTransientVariable

Returns a transient workflow variable with the specified name.

getTransientVariable(name: string): object

This function is a thin wrapper around the following .NET code: activityContext.GetTransientVariable(name).

getConfig

Provides access to a .NET configuration value.

getConfig(name: string): string

This is a security-sensitive function and is therefore not available by default. You need to enable this function through a setting. To enable this function, add the following code to your Startup class:

services.WithJavaScriptOptions(options => options.EnableConfigurationAccess = true);

As an example, let's say you have the following JSON in appsettings.json:

{
  "Elsa": {
    "Smtp": {
      "Host": "localhost",
      "Port": 2525
    }
  }
}

You can access the configured Port value using the following expression:

getConfig("Elsa:Smtp:Port") // returns '2525'

This function is a thin wrapper around the following .NET code: configuration.GetSection(name).Value where configuration is an instance of IConfiguration.

isNullOrWhiteSpace

Returns true if the specified string is null, empty or consists of white space only, false otherwise.

isNullOrWhiteSpace(value: string): boolean

This function is a thin wrapper around the following .NET code: string.IsNullOrWhiteSpace(value).

isNullOrEmpty

Returns true if the specified string is null or empty, false otherwise.

isNullOrEmpty(value: string): boolean

This function is a thin wrapper around the following .NET code: string.IsNullOrEmpty(value).

Workflow Functions

getWorkflowDefinitionIdByName

Returns the ID of the specified workflow by name. This is useful when for instance you are using the RunWorkflow activity, which requires the ID of the workflow definition to run.

getWorkflowDefinitionIdByName(name: string): string?

getWorkflowDefinitionIdByTag

Returns the ID of the specified workflow by tag. This is useful when for instance you are using the RunWorkflow activity, which requires the ID of the workflow definition to run.

getWorkflowDefinitionIdByTag(tag: string): string?

HTTP Functions

queryString

Returns the value of the specified query string parameter.

queryString(name: string): string

absoluteUrl

Converts the specified relative path into a fully-qualified absolute URL.

absoluteUrl(path: string): string

signalUrl

Generates a fully-qualified absolute signal URL that will trigger the workflow instance from which this function is invoked.

signalUrl(signal: string): string

Date/Time Functions

instantFromDateTimeUtc

Returns a new Instant object from the specified DateTime value.

Make sure that the DateTime value's Kind property is DateTimeKind.Utc.

currentInstant

Returns the current date/time value in the form of a NodaTime's Instant object.

currentInstant(): Instant

currentYear

Returns the current year.

currentYear(): number

startOfMonth

Returns the start of the month of the specified instant. If no instant is specified, the current instant is used.

startOfMonth(instant: Instant?): LocalDate;

endOfMonth(instant: Instant?)

Returns the end of the month of the specified instant. If no instant is specified, the current instant is used.

endOfMonth(instant: Instant?): LocalDate;

startOfPreviousMonth

Returns the start of the previous month of the specified instant. If no instant is specified, the current instant is used.

startOfPreviousMonth(instant: Instant?): LocalDate;

plus

Adds the specified Duration to the specified Instant and returns the result.

plus(instant: Instant, duration: Duration): Instant

minus

Subtracts the specified Duration from the specified Instant and returns the result.

minus(instant: Instant, duration: Duration): Instant

durationFromDays

Returns a duration constructed from the specified number of days.

durationFromDays(days: number): Duration

formatInstant

Formats the specified Instant using the specified format string and CultureInfo. If no culture info is provided, CultureInfo.InvariantCulture is used.

formatInstant(instant: Instant, format: string, cultureInfo: CultureInfo?): string

localDateFromInstant

Returns the LocalDate portion of the specified Instant.

localDateFromInstant(instant: Instant): LocalDate

instantFromLocalDate

Creates an Instant from the specified LocalDate value (start of date).

instantFromLocalDate(localDate: LocalDate): Instant

Additional Resources

To extend Elsa with your own functions and variables, see Extending JavaScript

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