Per-action modifiers array

[taye]

const restrictToParent = interact.modifiers.restrict({
  restriction: 'parent',
  elementRect: { left: 0, right: 0, top: 1, bottom: 1 },
})

const snap100x100 = interact.modifiers.snap({
  targets: [interact.snappers.grid({ x: 100, y: 100 })],
}),

interact(target).draggable({
  // apply the restriction, then the snap grid
  modifiers: [restrictToParent, snap100x100],
})

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Close #208