How to Write After Effects Expressions for ExtendScript
Writing After Effects scripts presents unique challenges, particularly when applying expressions to properties. While ExtendScript uses ES3 JavaScript, expressions can be written in modern JavaScript but must be passed as strings, creating formatting complications.
The Challenge
While ExtendScript relies on ES3 JavaScript, expressions can be written in modern JavaScript. But since expressions are not executed at the script level, you need to pass them along as a string.
Single-line expressions are straightforward, but multi-line expressions with indentation require extensive formatting work. This tedious approach obscures syntax highlighting and complicates revisions.
The Solution: Expressify
To address this problem, we created Expressify, an open-source tool that automatically compiles After Effects expressions into formatted JavaScript strings.
Key Features:
- Write expressions in modern JavaScript or copy directly from After Effects
- Save each expression as its own JavaScript file
- Automatically converts expressions into strings within a module pattern
- Generates an
ExpressionLib.jsfile for easy reference - Updates automatically when source files are added, deleted, or edited
Getting Started
You can download Expressify for free to streamline expression management in After Effects scripts.