@babel/plugin-proposal-do-expressions · BabelDetail The do { .. } expression executes a block (with one or many statements in it), and the final statement completion value inside the block becomes the completion value of the do expression. from You Don't Know JS, Types & Grammar -> Chapter 5 -> Section Statement Completion Values It can be seen as a complex version of the ternary operator: let a = do { if (x > 10) { ("big"); } else { ("smal
