Combining switch statements with destructuring [1] can be very useful: type ASTNode = { tag: 'BinOp', op: string, left: ASTNode, right: ASTNode }

Combining switch statements with destructuring [1] can be very useful: type ASTNode = { tag: 'BinOp', op: string, left: ASTNode, right: ASTNode } | { tag: 'UnaryOp', op: string, arg: ASTNode } | { tag: 'Literal', value: number }; function evaluate(node: ASTNode): number { switch (node.tag) { case 'BinOp': { const { op, left, right } = node; return evalBinary(op, evaluate(left), evaluate(right)); } case 'UnaryOp': { const { op, arg } = node; return evalUnary(op, evaluate(arg)); } case 'Literal': { const { value } = node; return value; } } } [1] https://ponyfoo.com/articles/es6-destructuring-in-depth https://ponyfoo.com/articles/es6-destructuring-in-depth