syntax: svg.append('line').attr({ x1: 0, x2: 2 * width / 4 })

[mootari]

From D3’s CHANGES.md:

For the sake of parsimony, the multi-value methods—where you pass an object to set multiple attributes, styles or properties simultaneously—have been extracted to d3-selection-multi and are no longer part of the default bundle.

¯\_(ツ)_/¯