During my coding journey, I encountered a situation where I was attempting to return an object from an arrow function. However, I noticed that the code snippet below was simply returning undefined. After some investigation, I determined that the curly braces were being interpreted as marking the beginning and end of the function body. What baffled me was why a: 1 did not result in an error.
const foo = () => {a: 1};
foo();
// > undefined
One of the main issues here is that the parser identifies a label named 'a' which is associated with the expression statement '1'. Without a return statement present, the resulting value will always be undefined.
However, if you encapsulate the body within parentheses, you will observe the object being correctly returned as shown below.
const foo = () => ({a: 1});
console.log(foo());
Additionally, by including the parentheses, you explicitly instruct the parser to interpret the object literal as an expression rather than a block statement.
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