Expression Troubleshooting

Introduction

This guide covers common After Effects expression errors and quick fixes. Follow these steps to troubleshoot, and find out how to ask for help if needed.

Most Common Issue

The wrong Expression Engine (ExtendScript) is being used. Fix: 1. Go to File > Project Settings > Expressions 2. Change the Expression Engine to JavaScript (available on AE 2019 and later.)

Other Common Issues

Typos or Case Sensitivity Errors: Double-check that variable or function names are spelled correctly and have the right case (JavaScript is case-sensitive).
Single Value Instead of an Array: If you assign a single value to properties that expect an array (e.g., Scale), you will get an error.

myScale = 5; // Incorrect
myScale = [5, 5]; // Correct
myScale = 5; s = [myScale, myScale]; // Another correct option

Missing Semicolons: Make sure to end each line with a semicolon ;
String vs. Variable Confusion: Listing a variable as a string when it shouldn’t be. Example: "myText" is a string, whereas myText is a variable.

When to ask for help?

If you tried everything above, and nothing still works. There are two things you can do:

You can download the tutorial project files that I usually provide for free on my Gumroad, and copy and paste my code into your projects to get it to work. From there, you can also compare what I have written and your code to see where is the mistake.
If you have to ask me for help, what I appreciate is having more context and description of your problem. For example:

Which lines does the error occurred?
What does the error(s) say?
What have you tried?
Have you consulted this guide and tried the solutions I mentioned?
What AE version are you running, and what OS.

Sample format for requesting troubleshooting

Hello, I having problem with line number. The error says errorMessage . I have tried solution but I still cannot fix the issue.

What doesn't help

Saying that "I wrote the code exactly" or I followed your tutorial. If it didn’t work, something else is likely wrong—usually a small typo.
Provide as much detail as possible so I can help you quickly.

More readings

How to troubleshoot expressions errors, Intro to Expression Rigs in After Effects, Zack Lovatt

PreviousJSX Cheatsheet NextUtilities

Last updated 1 month ago

Other Common Issues

Typos or Case Sensitivity Errors: Double-check that variable or function names are spelled correctly and have the right case (JavaScript is case-sensitive).

Single Value Instead of an Array: If you assign a single value to properties that expect an array (e.g., Scale), you will get an error.

myScale = 5; // Incorrect
myScale = [5, 5]; // Correct
myScale = 5; s = [myScale, myScale]; // Another correct option

Missing Semicolons: Make sure to end each line with a semicolon ;

String vs. Variable Confusion: Listing a variable as a string when it shouldn’t be. Example: "myText" is a string, whereas myText is a variable.

When to ask for help?

If you tried everything above, and nothing still works. There are two things you can do:

You can download the tutorial project files that I usually provide for free on my Gumroad, and copy and paste my code into your projects to get it to work. From there, you can also compare what I have written and your code to see where is the mistake.

If you have to ask me for help, what I appreciate is having more context and description of your problem. For example:

Which lines does the error occurred?

What does the error(s) say?

What have you tried?

Have you consulted this guide and tried the solutions I mentioned?

What AE version are you running, and what OS.

Sample format for requesting troubleshooting

Hello, I having problem with line number. The error says errorMessage . I have tried solution but I still cannot fix the issue.

What doesn't help

Saying that "I wrote the code exactly" or I followed your tutorial. If it didn’t work, something else is likely wrong—usually a small typo.

Provide as much detail as possible so I can help you quickly.