Wiki ▸ [[API Reference]] ▸ Behaviors

Behaviors encapsulate a complex set of low-level DOM interactions (i.e. user gestures that vary between input methods) into a higher-level set of custom events (see [[d3.dispatch|Internals#d3_dispatch]]). Behaviors often allow some additional configuration by the user. D3 includes two built-in behaviors:

  • [[Drag|Drag-Behavior]] — tracks mouse or multitouch movement(s) relative to an origin
  • [[Zoom|Zoom-Behavior]] — emits zoom and pan events in response to common input idioms

Behaviors are typically functions which you can apply to a selection using its [[call operator|Selections#call]]. For example, you can create and apply a behavior to a selection like this:'dragstart', function (d) {
  console.log("Started moving item with data:", d);

Note carefully the nesting: the 'dragstart' event is registered on the d3.behavior.drag() instance, not on the selection! It is this same instance — which is itself also a function — that gets called on the selection. This call allows the behavior to do its own internal setup on the selection.