JSFiddle - React, Tailwind, and code Playground
CoffeeScript
page = 'index/3'
console.log 'index for index: ' + page.indexOf 'index'
console.log 'index for thing: ' + page.indexOf 'thing'
console.log 'index for inde: ' + page.indexOf 'inde'
console.log 'index for any: ' + page.indexOf 'any'
if page.indexOf 'index' != -1 # does not contain index
console.log 'do index'
if page.indexOf 'thing' != -1 # does not contain index
console.log 'do thing'