On essaie une nouvelle approche... Mais sous Firefox, le premier chargement du...

$(window).on('load', function() {

    const start_prism_live_spip = function() {

        Bliss.$(".formulaire_spip .edition :not(.prism-live) > textarea").forEach(source => {

        const edition_textareas = document.querySelectorAll('.editer .edition textarea:not(.prism-live)');

        edition_textareas.forEach(function(source) {

            if (!Prism.Live.all.get(source)) {

                source.classList.add("language-#ENV{grammaire, spip_typo}");

                new Prism.Live(source);

            }

        });        

        })

        const editer_textareas = document.querySelectorAll('.editer > textarea:not(.prism-live)');

        editer_textareas.forEach(function(source) {

            if (!Prism.Live.all.get(source)) {

                source.classList.add("language-#ENV{grammaire, spip_typo}");

                new Prism.Live(source);

            }

        })

    }

    onAjaxLoad(start_prism_live_spip);

    start_prism_live_spip();