expression-utils.ts•3.03 kB
/**
* Utility functions for detecting and handling n8n expressions
*/
/**
* Detects if a value is an n8n expression
*
* n8n expressions can be:
* - Pure expression: `={{ $json.value }}`
* - Mixed content: `=https://api.com/{{ $json.id }}/data`
* - Prefix-only: `=$json.value`
*
* @param value - The value to check
* @returns true if the value is an expression (starts with =)
*/
export function isExpression(value: unknown): value is string {
return typeof value === 'string' && value.startsWith('=');
}
/**
* Detects if a string contains n8n expression syntax {{ }}
*
* This checks for expression markers within the string,
* regardless of whether it has the = prefix.
*
* @param value - The value to check
* @returns true if the value contains {{ }} markers
*/
export function containsExpression(value: unknown): boolean {
if (typeof value !== 'string') {
return false;
}
// Use single regex for better performance than two includes()
return /\{\{.*\}\}/s.test(value);
}
/**
* Detects if a value should skip literal validation
*
* This is the main utility to use before validating values like URLs, JSON, etc.
* It returns true if:
* - The value is an expression (starts with =)
* - OR the value contains expression markers {{ }}
*
* @param value - The value to check
* @returns true if validation should be skipped
*/
export function shouldSkipLiteralValidation(value: unknown): boolean {
return isExpression(value) || containsExpression(value);
}
/**
* Extracts the expression content from a value
*
* If value is `={{ $json.value }}`, returns `$json.value`
* If value is `=$json.value`, returns `$json.value`
* If value is not an expression, returns the original value
*
* @param value - The value to extract from
* @returns The expression content or original value
*/
export function extractExpressionContent(value: string): string {
if (!isExpression(value)) {
return value;
}
const withoutPrefix = value.substring(1); // Remove =
// Check if it's wrapped in {{ }}
const match = withoutPrefix.match(/^\{\{(.+)\}\}$/s);
if (match) {
return match[1].trim();
}
return withoutPrefix;
}
/**
* Checks if a value is a mixed content expression
*
* Mixed content has both literal text and expressions:
* - `Hello {{ $json.name }}!`
* - `https://api.com/{{ $json.id }}/data`
*
* @param value - The value to check
* @returns true if the value has mixed content
*/
export function hasMixedContent(value: unknown): boolean {
// Type guard first to avoid calling containsExpression on non-strings
if (typeof value !== 'string') {
return false;
}
if (!containsExpression(value)) {
return false;
}
// If it's wrapped entirely in {{ }}, it's not mixed
const trimmed = value.trim();
if (trimmed.startsWith('={{') && trimmed.endsWith('}}')) {
// Check if there's only one pair of {{ }}
const count = (trimmed.match(/\{\{/g) || []).length;
if (count === 1) {
return false;
}
}
return true;
}