Expression step reference

After reading this article, you’ll know the following:

• How to configure the Expression step

• What kind of expressions you can currently use

Expression step can be found in the Block Store and is used to create data formulas that help developers interact with various properties in their applications. Their values are changed depending on how the expressions are calculated.

After installing, drag the Expression step to its desired spot in the action flow and configure it.

We have a video about the basics of expressions as well that you might want to check out:

Configure the Expression step

Example:

Variables: 

Result: full_name: Dr. Odin van Eijk

Output type

In the result field, you can select whether you want the output type of the calculation to be provided to you in a text, boolean, number, object, or array variable.

After you select text as the output type, use the 'Result' field to define the name of the expression result. This result will then be available to you in the rest of your expression.

Example:

Variables:

List of available expressions

This is a list of expression formats that we currently support.

Text concatenation

For simple text concatenations with two variables, such as First name + Last name, you can also use this action step from the Block Store.

Advanced text concatenation

("{{ first_name }} " + ("{{ last_name_prefix }} " + "{{ last_name }}").trim()).length < 256 ? ("{{ first_name }} " + ("{{ last_name_prefix }} " + "{{ last_name }}").trim()) : {{ last_name }}

Variables:

Result (output type: Text): "John William De Graaf"

Ternary operator (if then else)

"{{ index }}" == 0 ? "{{ value }}" : "{{ some_other_value }}"

Output type: Depending on value

"{{ value }}" ? "{{ value }}" : "{{ some_other_value }}"

Output type: Depending on value

Present ternary

"{{ value }}" ? true : false

Output type: Boolean

Always return a numeric value

​{{ requested_id_value | 0 }}

Output type: Number

Result: Either a number from an existing ID or 0. This will prevent your action from going into error.

Ternary operator within a loop event

"{{ index }}" == 0 ? "{{ role_name }}" : "{{ current_role_names }}" + ", " + "{{ role_name }}"

Result (output type: Text): "Admin, Employee, Manager"

Concatenate collection, comma-separated

"{{ roles.map(item => item.name) }}"

Result (output type: Text): "Admin, Employee, Manager"

Concatenate collection, custom separator

"{{ roles.map(item => item.name) }}".replaceAll(",", "|")

Result (output type: Text): "Admin|Employee|Manager"

Concatenate filtered collection, custom separator

"{{ roles.filter(item => item.id < 3).map(item => item.name) }}".replaceAll(",", "|")

Result (output type: Text): "Admin|Employee"

Get URL and name from a file property

"{{{ file.url }}}"

Result (output type: Text): "https://assets.bettyblocks.com/.../…/example.pdf"

"{{{ file.name }}}"

Result (output type: Text): "example.pdf"

Using Regex

Regex expressions use Regex formatting in combination with JavaScript to filter results from text, and if the filtered result is found, it will be returned to your action step as the result. To learn how you can define Regex, there as websites like Regexr, that can help you create the perfect Regex condition for your use case.

When working with conditional whitespaces, make sure to double the "\" in your expression. For example, when a zip code could be either 1234AB or 1234 AB . The "\\s" option will allow you to filter when a whitespace is or isn't allowed to be there.

"{{ value }}".replaceAll("r", "t")

"{{{ value }}}".replace(/<[^>]*>?/gm, '')

Truncate

"{{ value }}".length > {{ limit }} ? "{{ value }}".substring(0, {{ limit }}) + '...' : "{{ value }}"

Sum

{{ index }} + 1

Multiply

{{ index }} * 2

Count collection

{{ orderlines.map(item => item.line_price).reduce((a, b) => a + b, 0) }}

new Date().toISOString().substring(0,10)

new Date("{{ date }}").toLocaleDateString("{{ locale }}", {{ options }})

new Date("2022-12-23T08:41:50Z").toLocaleDateString("nl-NL", { weekday: 'long', year: 'numeric', month: 'short', day: 'numeric' })

Beginning of month

Returns the first day of a given month.

(() => {
  const dateObj = new Date("");
  return new Date(dateObj.getFullYear(), dateObj.getMonth(), 1).toLocaleDateString("en-CA");
})();

Variables:

Result (output type: Text): "2025-02-01"

End of month

(() => { 
  const dateObj = new Date(""); 
  return new Date(dateObj.getFullYear(), dateObj.getMonth() + 1, 0).toLocaleDateString("en-CA");
})();

Variables:

Result (output type: Text): "2025-02-28"

Others

Simple JavaScript function

It's also possible to use native JavaScript functions without interpolating values. In the example below, we are generating a random 5-digit code.

Math.floor(Math.random() * 90000) + 10000;

Result (output type: Number): 65427

Loop through collection with results

"<ul>{{#names}}<li>{{ name }}</li>{{/names}}</ul>{{^names}}Sorry, no people to list!{{/names}}"

"<ul>{{#names}}<li>{{../fullName}}</li>{{/names}}</ul>"

"<ul>{{#names}}<li>{{ name }}</li>{{/names}}</ul>{{^names}}Sorry, no people to list!{{/names}}"

"{{ customer_name }}"

"{{{ customer_name }}}"

"<p>This is shown!{{#show}} Psst, this is never shown{{/show}}</p>"

Show comments

"This is shown!{{#show}} And, this is also shown{{/show}}"

Format phone number

Format a phone number to a certain format, in this format, the first 3 letters are separated (the location code) and surrounded by brackets ().

function formatPhoneNumber() { 
  // Return empty text if there is no phone number 
  if (!"") return ""; 

  // Only get numbers from text 
  const onlyNumbers = "".replace(/[^0-9]/g, ""); 
  
  // Format phone number like "(123) 456-7890" 
  return "(" + onlyNumbers.substring(0, 3) +") " + onlyNumbers.substring(3,6) +"-" + onlyNumbers.substring(6, 10); 
}();

Variables:

Key	Value
office_phone	1234567890

Result (output type: Text): “(123) 456-7890”

 

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Monday of week

Retrieve the date of a Monday from a week and year you provide.

function getMondayOfWeek() { 
  const date = new Date(2025, 0, (1 + ( - 1) * 7)); 
  const offset = date.getTimezoneOffset(); 
  return new Date(date.getTime() - (offset * 60 * 1000)).toISOString().split('T')[0]; 
}();

Variables:

Key	Value
year	2024
week_number	25

Result (output type: Text): “2024-06-17”

This date value can be saved in a date property and can be used further in the action flow.

 

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Get element from array

Get a specific element from an array given an index (number).

Important to know that the index count starts from 0, therefore index 1 will return the second value from your array.

“{{ array }}“.split(“,”)[{{ index }}]

Variables:

Key	Value
array	[“Element 1", “Element 2”, “Element 3"]
index	1

Result (output type: Text): “Element 2”

 

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Filter record from collection

This filter expression is used to filter an element from a (custom) collection. In this example, the output type array is used.

The expression itself is a good example of how you can deal with collections in the Expression step.

[{{ collection.map(item => item.id) }}].filter(item => item !== {{ record_id }})

Variables:

Key	Value
collection	[{ id: 1, title: “Element 1" }, { id: 2, title: "Element 2" }, { id: 3, title: “Element 3” }]
record_id	2

Result (output type: Array): [{ id: 1, title: “Element 1" }, { id: 3, title: “Element 3” }]

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Some expressions have also been turned into a block. Have a look at this list to see what steps are already available in the Block Store.

If you have any expression formatting you would like to report and add to the list, reach out to us via email: vitalii.nemchenko@bettyblocks.com