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FormatError SyntaxError .

message name stack .

          let err = new FormatError("formatting error");

alert( err.message ); // formatting error
alert( err.name ); // FormatError
alert( err.stack ); // stack

alert( err instanceof FormatError ); // true
alert( err instanceof SyntaxError ); // true (  SyntaxError  )
        

class FormatError extends SyntaxError {
  constructor(message) {
    super(message);
    this.name = this.constructor.name;
  }
}

let err = new FormatError("formatting error");

alert( err.message ); // formatting error
alert( err.name ); // FormatError
alert( err.stack ); // stack

alert( err instanceof SyntaxError ); // true