Two-way Binding is a Two-way Street

Two-way binding in frontend frameworks is a divisive topic. It reduces boilerplate by automatically syncing state between parent and child components, but introduces risks around implicit mutations, unclear ownership, and hard-to-trace update loops. The post examines three approaches to managing these risks: explicit opt-in (Svelte's bind: syntax), internal read/write segregation via events (Vue's v-model), and full read/write separation that avoids two-way binding entirely (React and SolidJS). The author, creator of SolidJS, personally favors the no-two-way-binding approach and outlines red flags to watch for in framework design, such as implicit binding, mutable primitives passed freely, and writing to props in deeply reactive systems.