Expression Syntax

Expressions are strings used by properties such as visibleIf, enableIf, requiredIf, defaultValueExpression, setValueExpression, choicesVisibleIf, validators, and calculated values.

Referencing Values

Use curly braces around question or calculated value names.

{
  "visibleIf": "{hasPets} = true"
}

Common Operators

• Equality: {country} = 'AU'
• Not equal: {country} != 'AU'
• Comparison: {age} >= 18
• And: {age} >= 18 and {country} = 'AU'
• Or: {contactMethod} = 'email' or {contactMethod} = 'phone'
• Empty check: {email} notempty

Common Patterns

Conditional question

{
  "type": "comment",
  "name": "details",
  "title": "Tell us more",
  "visibleIf": "{needsFollowUp} = true"
}

Required only when visible

{
  "type": "text",
  "name": "email",
  "title": "Email",
  "inputType": "email",
  "requiredIf": "{contactMethod} = 'email'"
}

Calculated value

{
  "name": "total",
  "expression": "{quantity} * {unitPrice}"
}

Dynamic default

{
  "type": "text",
  "name": "dueDate",
  "inputType": "date",
  "defaultValueExpression": "today(7)"
}