How deeply does D3.js in Action, Third Edition cover classed()?

Explains the two arguments, contrasts classed() with attr(), and demonstrates Boolean callbacks for per-element class changes.

Classed()

As explained in D3.js in Action, Third Edition

classed() is a D3 selection method that adds or removes a specified CSS class on each selected element according to a Boolean value.

classed() is a D3 selection method for adding or removing one CSS class without overwriting the selection’s other classes. Pass the class name first and true or false second. section 7.2.2

Unlike attr("class", ...), which replaces the entire class attribute, classed() changes a named class independently. This preserves an existing class such as filter while toggling active. section 7.2.2

Marking the active filter

d3.selectAll(".filter") .classed("active", filter => filter.id === d.id ? true : false); A click callback updates each filter button so only the clicked filter receives the active class, then refreshes the histogram. section 7.2.1

myActiveFilter
  .classed("active", true);

Shows the compact form for adding the active class while retaining the existing filter class. section 7.2.2

How D3.js in Action, Third Edition covers it

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Related concepts

booleanuses · A Boolean is a logical type or value representing truth or falsity, conventionally with two states: true and false.
selection.attr()alternative to · A D3 selection method that gets or sets attributes on elements in a selection, optionally deriving values from bound data.
class attributeconfigures · The class attribute is an HTML attribute whose space-separated values assign one or more class names to an element.
on()uses · on() is a D3 selection method that registers an event listener for a specified event type and callback function.
selectionuses · A D3 selection is an object representing one or more selected document elements on which D3 operations can be performed.

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.