Marc Backes

Under The Hood Of Vue 3 Reactivity

What if you could build Vue 3's reactivity from scratch? See how ES6 Proxies make it possible in under 30 lines of code.

Under The Hood Of Vue 3 Reactivity
#1about 3 minutes

Understanding the core principles of reactivity

Reactivity is explained as an automated observer pattern where changes to data trigger updates wherever that data is used.

#2about 2 minutes

Using ES6 Proxies to intercept data access

ES6 Proxies wrap objects and allow interception of operations like getting or setting properties, which is the foundation for Vue 3's reactivity.

#3about 4 minutes

Architecting the reactivity system with maps and sets

The system uses a WeakMap to store a Map for each object, which in turn stores a Set of effects for each property.

#4about 5 minutes

Demonstrating the problem with manual state updates

The initial code shows how changing a product's price or quantity requires manually recalculating the total each time.

#5about 3 minutes

Building manual track and trigger functions

The `track` function adds an effect to a Set, and the `trigger` function iterates over the Set to execute all tracked effects.

#6about 11 minutes

Building a reactive function with ES6 Proxies

A `reactive` function is created using an ES6 Proxy to intercept property access, with `get` handlers calling `track` and `set` handlers calling `trigger`.

#7about 4 minutes

Automating dependency tracking with an effect function

The `effect` function wraps a piece of code, sets it as the `activeEffect`, and runs it once to automatically track all accessed reactive properties.

#8about 6 minutes

Connecting the reactive system to the DOM

The final step demonstrates the complete system by linking the reactive state to DOM elements, which update automatically when the state changes.

#9about 12 minutes

Answering audience questions about reactivity and career

The speaker answers questions about proxy performance, nested objects, career journey, and identifying reactive objects in a large codebase.

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