Dangerous JS — Conditions

eSheet supports three condition modes for driving field visibility, enabled state, and required state. Two are safe (no JS execution); one requires the dual opt-in gate.

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Condition Modes Overview

Mode	conditionType	Requires dangerous JS?	When to use
Field	'field'	No	Direct comparison against another field's value
Expression	'expression'	No	Arithmetic or boolean logic across multiple fields
JS	'js'	Yes	Complex logic, date windows, arbitrary JavaScript

All three modes are evaluated inside a ConditionalRule:

effect: visible
logic: AND
conditions:
  - conditionType: field
    targetId: pain-level
    operator: greaterThan
    expected: '3'

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Field Conditions (conditionType: 'field')

Reference another field's response directly. Does not require dangerous JS.

conditionType: field
targetId: has-allergies
operator: equals
expected: 'Yes'

Available operators:

Operator	Description
equals	Value equals expected
notEquals	Value does not equal expected
contains	String contains expected substring
includes	Array includes expected item
empty	Value is empty / unanswered
notEmpty	Value is present / answered
greaterThan	Numeric value > expected
greaterThanOrEqual	Numeric value >= expected
lessThan	Numeric value < expected
lessThanOrEqual	Numeric value <= expected

Property accessor — use .length or .count on array responses:

conditionType: field
targetId: symptoms
operator: greaterThan
expected: '2'
propertyAccessor: count

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Expression Conditions (conditionType: 'expression')

Use eSheet's safe expression evaluator. Does not require dangerous JS.

• Field references use {fieldId} syntax
• Supports arithmetic (+, -, *, /, %), comparison (==, !=, <, <=, >, >=), and logical (&&, ||, !) operators
• Supports {fieldId}.length and {fieldId}.count property accessors
• Does not use new Function — evaluation is sandboxed by design
• Works even when dangerous JS is disabled

conditionType: expression
expression: '{temperature} >= 38 && {symptoms}.count > 1'

conditionType: expression
expression: "{total-score} >= 8 || {override-flag} == 'Yes'"

For most business rules, expression conditions are sufficient. Use JS conditions only when the logic requires function calls, date manipulation, or external data.

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JS Conditions (conditionType: 'js')

Arbitrary JavaScript for complex conditional logic. Requires dangerouslyAllowJS: true in the schema and allowDangerousJS={true} on the host component.

Schema

id: followup-section
fieldType: section
rules:
  - effect: visible
    logic: AND
    conditions:
      - conditionType: js
        expression: responses['has-symptoms'] === 'Yes' && new Date() > new Date(responses['onset-date'])

The expression must evaluate to a truthy value for the condition to pass. If dangerouslyAllowJS is disabled, conditionType: 'js' always evaluates as false.

Expression Context

Every JS condition receives two arguments:

responses

A flat Record<string, unknown> — same shape as calculations:

Field type	responses['id'] value
text / longtext	Number if parseable, otherwise raw string
radio / dropdown	Option score (if set), otherwise option value string
check / multiselectdropdown	Array of selected values (or scores if any are set)
rating / slider	Option score or numeric value
boolean	Option value string ('Yes' / 'No' by default)
All others	Raw answer string

The internal call signature is:

new Function('responses', 'return ' + expression)(data);

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Examples

Date window — PPD read date

Replaces legacy moment.js date range conditionals (moment(date).isBetween(...)):

conditionType: js
expression: (() => { const tested = new Date(responses['ppd-date-tested']); if (!tested || isNaN(tested)) return false; const now = new Date(); const diffDays = (now - tested) / (1000 * 60 * 60 * 24); return diffDays >= 2 && diffDays <= 8; })()

Today relative date comparisons

Replaces legacy todayIsAfter(), todayIsBefore(), todayIsBetween(), todayIsDate():

conditionType: js
expression: new Date() > new Date('2019-06-24')

conditionType: js
expression: new Date() < new Date('2007-02-13')

conditionType: js
expression: new Date() >= new Date('2019-12-15') && new Date() <= new Date('2020-03-25')

Multi-OR: show if yes was answered to any of several fields

Replaces legacy multi-observationDisplay OR chains:

effect: visible
logic: OR
conditions:
  - conditionType: js
    expression: responses['fatigue-field'] === 'Yes'
  - conditionType: js
    expression: responses['sleep-problems-field'] === 'Yes'
  - conditionType: js
    expression: responses['sleeping-aids-field'] === 'Yes'

Or equivalently with a single JS condition:

conditionType: js
expression: "['fatigue-field', 'sleep-problems-field', 'sleeping-aids-field'].some(id => responses[id] === 'Yes')"

Show if any observation is answered (not empty, not zero)

Replaces legacy observationValueByName('name') && observationValueByName('name') !== 0:

conditionType: js
expression: responses['pain-scale'] !== '' && responses['pain-scale'] !== 0

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Legacy Migration Reference

Legacy function / pattern	eSheet equivalent
observationValueByName('name')	responses['field-id'] (within-form field reference)
jQuery.inArray(val, arr) > -1	arr.includes(val) in JS condition
miearray.inSet(val, arr)	arr.includes(val) in JS condition
todayIsAfter('date')	new Date() > new Date('date')
todayIsBefore('date')	new Date() < new Date('date')
todayIsBetween('d1', 'd2')	new Date() >= new Date('d1') && new Date() <= new Date('d2')
todayIsDate('date')	new Date().toDateString() === new Date('date').toDateString()
Moment.js isBetween	Native Date arithmetic — see PPD date window example above

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Builder UI

When allowDangerousJS={true} is passed to <EsheetBuilder> and the loaded schema has dangerouslyAllowJS: true, the Logic Editor's condition row shows a JS tab alongside Field and Expression condition modes.