tell application "Safari"
    'window.find()' command change the scroll position when it select the founded string
    set scrollPos to do JavaScript "document.designMode = 'on'; [window.pageXOffset.toString(),window.pageYOffset.toString()]" in document 1
    repeat with thisText in myList
        do JavaScript "var sel = window.getSelection();n                sel.collapse(document.body, 0);//------    To start at the beginning of the document, not after the selectioned textn                while (window.find('" & thisText & "', true)) {document.execCommand('HiliteColor', false, '#5cdf64');}n                sel.collapseToEnd()" in document 1
    end repeat

    -- restore the scroll position
    do JavaScript "document.designMode = 'off';  window.scrollTo(" & (item 1 of scrollPos) & ", " & (item 2 of scrollPos) & ")" in document 1
end tell

repeat with thisText in myList
    execute javascript "var sel = window.getSelection();n                sel.collapse(document.body, 0);//------    To start at the beginning of the document, not after the selectioned textn                while (window.find('" & thisText & "', true)) {document.execCommand('HiliteColor', false, '#5cdf64');}n                sel.collapseToEnd()"
end repeat
execute javascript "document.designMode = 'off';  window.scrollTo(" & (item 1 of scrollPos) & ", " & (item 2 of scrollPos) & ")"

tell application "Google Chrome"
    execute tab 3 of window 1 javascript "document.designMode = 'on'; [window.pageXOffset.toString(),window.pageYOffset.toString()]"
        --> {"0", "0"}
    execute current application javascript "var sel = window.getSelection();n                sel.collapse(document.body, 0);//------    To start at the beginning of the document, not after the selectioned textn                while (window.find('AppleScript', true)) {document.execCommand('HiliteColor', false, '#5cdf64');}n                sel.collapseToEnd()"
        --> missing value
    execute current application javascript "var sel = window.getSelection();n                sel.collapse(document.body, 0);//------    To start at the beginning of the document, not after the selectioned textn                while (window.find('2018', true)) {document.execCommand('HiliteColor', false, '#5cdf64');}n                sel.collapseToEnd()"
        --> missing value
    execute current application javascript "var sel = window.getSelection();n                sel.collapse(document.body, 0);//------    To start at the beginning of the document, not after the selectioned textn                while (window.find('CLOSED', true)) {document.execCommand('HiliteColor', false, '#5cdf64');}n                sel.collapseToEnd()"
        --> missing value
    execute current application javascript "document.designMode = 'off';  window.scrollTo(0, 0)"
        --> missing value
end tell
Result:
missing value