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Well - charts in JS is OK for user but NOT ok for bots. Hiding text is "devalued" them and also not ok for bots. Probably the best is if you use some tool as PhantomJS and make static image of charts. Can be PNG or JPG with lot of text (alt and title) that describing what is this image. I know that this wasn't answer you're expecting, but bots can't see everything that JavaScript make. I forgot... MOZ have same issue with their WBF - text and video only. So look strange for bots. From two years they make text representation of video too. Now layout is text-video-text-text-text-text. Seems that works for them. So mine idea is try to make chart and below make text representation of what is in this charts with lot of text. Bots love this (and humans too!) and you can leave JS code then.