You cannot declare function declaration using ES6 arrow function. Arrow functions are meant to be replacement for traditional function expressions. // traditional function expression var foo = function () { return 'foo' ; }; // ES6 arrow function var foo = () => ({}); // single line must be surrounded with parenthesis var bar = () => 'bar' ; // single line do not need return keyword var baz = () => { return 'baz' ; // multiline needs explicit return keyword }; In order to better understand the functions I would highly recommend this article https://kangax.github.io/nfe/