SyntaxError: function statement requires a name

The JavaScript exception "function statement requires a name" occurs when there is a function statement in the code that requires a name.

Message#

SyntaxError: Function statements require a function name (V8-based)
SyntaxError: function statement requires a name (Firefox)
SyntaxError: Function statements must have a name. (Safari)

Error type#

{{jsxref("SyntaxError")}}

What went wrong?#

There is a function statement in the code that requires a name. You'll need to check how functions are defined and if you need to provide a name for it, or if the function in question needs to be a function expression, an IIFE, or if the function code is placed correctly in this context at all.

Examples#

Statements vs. expressions#

A function statement (or function declaration) requires a name. This won't work:

```js-nolint example-bad function () { return "Hello world"; } // SyntaxError: function statement requires a name

You can use a [function expression](/en-US/docs/Web/JavaScript/Reference/Operators/function) (assignment) instead:

```js example-good
const greet = function () {
  return "Hello world";
};

If your function is intended to be an IIFE (Immediately Invoked Function Expression, which is a function that runs as soon as it is defined) you will need to add a few more braces:

```js example-good (function () { // … })();

### Labeled functions

[Labels](/en-US/docs/Web/JavaScript/Reference/Statements/label) are an entirely different feature from function names. You can't use a label as a function name.

```js-nolint example-bad
function Greeter() {
  german: function () {
    return "Moin";
  }
}
// SyntaxError: function statement requires a name

In addition, labeled function declarations themselves are a deprecated feature. Use regular function declarations instead.

```js example-good function Greeter() { function german() { return "Moin"; } }

### Object methods

If you intended to create a method of an object, you will need to create an object.
The following syntax without a name after the `function` keyword is valid then.

```js example-good
const greeter = {
  german: function () {
    return "Moin";
  },
};

You can also use the method syntax.

const greeter = {
  german() {
    return "Moin";
  },
};

Callback syntax#

Also, check your syntax when using callbacks. Braces and commas can quickly get confusing.

```js-nolint example-bad promise.then( function () { console.log("success"); }); function () { console.log("error"); } // SyntaxError: function statement requires a name

Correct would be:

```js example-good
promise.then(
  function () {
    console.log("success");
  },
  function () {
    console.log("error");
  },
);

See also#

• Functions guide
• function
• function expression
• {{Glossary("IIFE")}}
• Labeled statement