SyntaxError: Unexpected token
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The JavaScript exceptions "unexpected token" occur when the parser does not see a token it recognizes at the given position, so it cannot make sense of the structure of the program. This might be a simple typo.
Message#
SyntaxError: Unexpected token ';' (V8-based)
SyntaxError: Unexpected identifier 'x' (V8-based)
SyntaxError: Unexpected number (V8-based)
SyntaxError: Unexpected string (V8-based)
SyntaxError: Unexpected regular expression (V8-based)
SyntaxError: Unexpected template string (V8-based)
SyntaxError: unexpected token: identifier (Firefox)
SyntaxError: expected expression, got "x" (Firefox)
SyntaxError: expected property name, got "x" (Firefox)
SyntaxError: expected target, got "x" (Firefox)
SyntaxError: expected meta, got "x" (Firefox)
SyntaxError: expected rest argument name, got "x" (Firefox)
SyntaxError: expected closing parenthesis, got "x" (Firefox)
Error type#
{{jsxref("SyntaxError")}}
What went wrong?#
A specific language construct was expected, but something else was provided. This might be a simple typo.
Examples#
Expression expected#
For example, when chaining expressions, trailing commas are not allowed.
```js-nolint example-bad for (let i = 0; i < 5,; ++i) { console.log(i); } // Uncaught SyntaxError: expected expression, got ';'
Correct would be omitting the comma or adding another expression:
```js example-good
for (let i = 0; i < 5; ++i) {
console.log(i);
}
Not enough parentheses#
Sometimes, you leave out parentheses around if statements:
``js-nolint example-bad
function round(n, upperBound, lowerBound) {
if (n > upperBound) || (n < lowerBound) { // Missing parentheses here!
throw new Error(Number ${n} is more than ${upperBound} or less than ${lowerBound}`);
} else if (n < (upperBound + lowerBound) / 2) {
return lowerBound;
} else {
return upperBound;
}
} // SyntaxError: expected expression, got '||'
The parentheses may look correct at first, but note how the `||` is outside the
parentheses. Correct would be putting parentheses around the `||`:
```js-nolint example-good
function round(n, upperBound, lowerBound) {
if ((n > upperBound) || (n < lowerBound)) {
throw new Error(
`Number ${n} is more than ${upperBound} or less than ${lowerBound}`,
);
} else if (n < (upperBound + lowerBound) / 2) {
return lowerBound;
} else {
return upperBound;
}
}
A structure error further up confused the meaning#
Sometimes, the error is caused by some structure issues not directly next to the error location, so you need to look around for potential errors. For example, you intended to declare a method of an object, but you declared it as a property instead:
```js-nolint example-bad const MyComponent = { mounted: { document.getElementById("app").classList.add("loaded"); } }
The `.` after `document` is unexpected, because JavaScript is parsing the `{}` as an object literal instead of a function body, so it expects a `:`. The problem is solved by declaring `mounted` as function.
```js-nolint example-good
const MyComponent = {
mounted() {
document.getElementById("app").classList.add("loaded");
}
}
See also#
- {{jsxref("SyntaxError")}}