SyntaxError: Unexpected end of input – Causes and Fixes [GAS / JavaScript]

When writing JavaScript or Google Apps Script (GAS), you may encounter an error like this:

SyntaxError: Unexpected end of input

This article explains why this error occurs and how to fix it, with practical patterns that developers commonly encounter. We'll focus on the pain points where GAS and JavaScript beginners often stumble, with solutions to prevent recurrence.

What Does SyntaxError: Unexpected end of input Mean?

In short, this error means:

"Your code ends prematurely (something is not closed)."

JavaScript's parser expects the code to continue, but the code ends unexpectedly. This causes the error.

Common Cause #1: Forgot to Close Curly Braces {}

This is the most frequent cause.

Example: Missing closing brace in a function

function test() {
  Logger.log("test");

Missing one }.

Example: Missing closing brace in an if statement

function check() {
  if (true) {
    Logger.log("OK");
}

Missing one }.

How to Fix It

• When you write {, immediately write }
• Use your editor's indentation features
• Use bracket-matching features

function test() {
  Logger.log("test");
}

Common Cause #2: Forgot to Close Parentheses ()

This commonly occurs in function calls and conditional expressions.

Example: Unclosed function call

Logger.log("Hello"

Missing ).

Example: Unclosed conditional expression

if (x > 10 {
  Logger.log("OK");
}

Missing ) in the if condition.

How to Fix It

• Close parentheses immediately after opening them
• Use editor autocomplete

Logger.log("Hello");

if (x > 10) {
  Logger.log("OK");
}

Common Cause #3: Forgot to Close Square Brackets []

This occurs in array definitions or object access.

Example: Unclosed array definition

const list = [1, 2, 3

Missing ].

How to Fix It

• Close arrays immediately after defining them

const list = [1, 2, 3];

Common Cause #4: Unclosed String Quotes

The string definition is incomplete.

Example: Unclosed double quotes

const message = "Hello World
Logger.log(message);

Missing closing ".

How to Fix It

• Always close strings with matching quotes
• Use template literals (backticks) for multi-line strings

const message = "Hello World";
Logger.log(message);

// For multi-line
const multiLine = `
  Line 1
  Line 2
`;

Common Cause #5: Deep Nesting Makes Matching Difficult

In complex code, it can become unclear which bracket closes where.

Example: Deep nesting structure

function main() {
  if (true) {
    for (let i = 0; i < 10; i++) {
      if (i % 2 === 0) {
        Logger.log(i);
      }
    }
  // Missing } here
}

How to Fix It

• Keep indentation properly aligned
• Use your editor's code folding feature
• Extract complex logic into separate functions

function main() {
  if (true) {
    for (let i = 0; i < 10; i++) {
      if (i % 2 === 0) {
        Logger.log(i);
      }
    }
  }
}

Common Cause #6: Incomplete Code from Copy-Paste

When copying and pasting code, the last part may be missing.

How to Fix It

• Check the entire copied code
• Verify bracket matching

Basic Debugging Checklist

When you encounter SyntaxError: Unexpected end of input, check these points in order:

1. Do the numbers of { and } match?
2. Do the numbers of ( and ) match?
3. Do the numbers of [ and ] match?
4. Are string quotes closed?
5. Is indentation properly aligned?
6. Is copied code complete?

These six points solve most cases.

Best Practices to Prevent This Error

// Close brackets immediately after opening
function test() {
  // Write code here
}

// Keep indentation aligned
if (true) {
  Logger.log("OK");
}

// Use editor auto-formatting features

Using Visual Studio Code or Apps Script Editor

Most editors have features to check bracket matching:

• Bracket highlighting
• Indentation guides
• Autocomplete
• Syntax checking

Using these features helps prevent errors.

Summary

SyntaxError: Unexpected end of input means "something is not closed."

In GAS especially, just being aware of:

• Function curly braces
• Conditional parentheses
• Array square brackets

can drastically reduce how often this error occurs.

When this error appears, the first step is to check "do the bracket counts match?" Make full use of your editor's features for comfortable coding.