This error appears when the JavaScript parser encounters something that “should not exist” at that position. In practice, the causes are highly predictable. Here is the compact checklist I use in real GAS development projects.

■ 1. Missing commas or brackets

The most common cause.

const obj = {
  name: "Taro"
  age: 20  // missing comma
};

Check:

• commas in objects/arrays
• missing ) or }
• unclosed if, for, or function blocks

■ 2. Unclosed template literals

const text = `Hello ${name};

If the closing backtick is missing, everything breaks.

■ 3. Variable declaration glitches

Missing semicolons or declaring the same const twice may trigger this.

■ 4. Invisible full-width spaces

Copied code may contain Unicode spaces:

const　name = "Taro"; // full-width space

■ 5. Unsupported syntax in GAS

GAS does not support import, export, or require.

■ 6. Quickest real-world fix flow

1. Check the line and the line above it.
2. Look for missing comma, bracket, or backtick.
3. Delete and manually rewrite the suspicious part.
4. Run auto-formatting (Ctrl+Shift+I).
5. Test with small logs.

■ 7. Before/After example

Before (error):

const user = {
  name: "kazu"
  email: "test@example.com"
}

After:

const user = {
  name: "kazu",
  email: "test@example.com",
};

Ref

1. JavaScript SyntaxError — MDN
   https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Unexpected_identifier
2. Google Apps Script – JavaScript Language Features
   https://developers.google.com/apps-script/guides/services/javascript