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

SyntaxError

IIFE

function function

function () {
  return "Hello world";
}
// SyntaxError: function statement requires a name

function

const greet = function () {
  return "Hello world";
};

IIFE

(function () {
  // 
})();

function Greeter() {
  german: function () {
    return "Moin";
  }
}
// SyntaxError: function statement requires a name

function Greeter() {
  function german() {
    return "Moin";
  }
}

function

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

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

promise.then(
  function () {
    console.log("success");
  });
  function () {
    console.log("error");
}
// SyntaxError: function statement requires a name

promise.then(
  function () {
    console.log("success");
  },
  function () {
    console.log("error");
  },
);

MDN

MDN 2026217

GitHub