GTM JavaScript Coding Standards

This skill ensures all JavaScript code generated for Google Tag Manager (GTM) Custom HTML tags is ES5-compliant and follows current best practices (2024-2025).

Critical Constraint: ES5 Only

GTM's JavaScript compiler operates in ES5 (ECMAScript 5) mode by default. ES6+ syntax causes compilation errors and prevents tag publishing.

Prohibited ES6+ Features

NEVER use these in GTM Custom HTML tags: