JSFiddle - React, Tailwind, and code Playground
HTML
<span>The quick brown fox jumps over the lazy dog</span>
CoffeeScript
$(document).ready ->
container = $('span')
container.click (e) ->
container_width = container.width()
char_width = p_width / container.text().length
position_inside = e.pageX - container.offset().left
console.log("#{ Math.floor(position_inside / char_width) - 1 }")