Ref

As explained in D3.js in Action, Third Edition

A React ref is an object or callback mechanism that provides access to a rendered component or DOM element.

A React ref gives code access to a rendered element so another tool, such as D3, can control that element directly. With useRef(), attach the ref to an element, then read its current property after rendering. section 8.5.1

Use a ref to connect React-rendered markup with D3:

• Import useRef and useEffect from React, then initialize a ref such as scatterplotRef = useRef(). section 8.5.1
• Attach the ref to the element D3 should control, for example <g ref={scatterplotRef}></g>. section 8.5.1
• Inside useEffect, select the current rendered element with d3.select(scatterplotRef.current). section 8.5.1
• Keep D3 operations inside the effect so they work with the up-to-date rendered element. section 8.5.1

Animating a curve path

A hybrid chart can let React render a path while a ref lets D3 animate its d attribute. The effect selects pathRef.current, applies a transition, and reruns when the data or line generator changes. section 8.7

Figure 8.5 To let D3 control a portion of the DOM in React, we first need to import the useRef() and the useEffect() hooks into our component. We then initialize a ref and attach it as an attribute to the element we want to control with D3. Finally, inside a useEffect() hook, we select the current instance of the ref and start using D3 as usual.

The diagram shows the complete handoff: initialize useRef, attach the ref, select its current element inside useEffect, and continue with D3. section 8.5.1

How D3.js in Action, Third Edition covers it

How deep it goes

Explains initialization, attachment, current-element selection, and effect placement through chart implementations.

Examples

Uses a D3-controlled scatterplot and a hybrid rankings visualization with animated curve paths.

What you can do after

Apply it via useRef, useEffect, and D3 to select and animate rendered chart elements.

How it connects

Links React hooks, useEffect, D3 selections, DOM elements, SVG paths, and transitions.

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Also explained in

• 

  liveBookmanning.com
  React Hooks in Action: With Suspense and Concurrent ModeA React ref is a persistent mutable object that provides access to a value, commonly a rendered DOM element, through its current property.
• 

  liveBookmanning.com
  React in DepthA React ref is a special property that provides access to a rendered DOM node or component instance rather than being handled as an ordinary component prop.

Compare how 3 books explain ref →

Related concepts

• useRefproduced by · useRef is a React Hook that returns a persistent mutable object whose current property can hold a value across renders without causing re-rendering when changed.
• attributehas part · An attribute is a named property, value, or piece of information associated with an entity, object, or program element.
• component re-renderingcontrasts with · Component re-rendering is the repeated execution of a component’s rendering logic to produce updated user-interface output after relevant data changes.
• text boxuses · A text box is an interactive user-interface control for entering, displaying, or editing text.
• Reactused by · React is an open-source JavaScript library for building user interfaces from declarative, reusable components.

This explainer was generated by Manning's knowledge graph from the text of D3.js in Action, Third Edition. The section links point to the parts of the book it draws on.