create d3.js axes without numbering

The simplest way to hide tick labels is via CSS:

.axis text { display: none; }

Alternatively, you could use the empty string as the tick format:

axis.tickFormat("");

Or, you could use post-selection to remove the text elements after creating the axis:

selection.call(axis).selectAll("text").remove();

Of course, I prefer CSS as it's the most declarative. Example here:

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