If you want to be able to do this anywhere on a page, you need to be able to set some kind of identifying ID to your selection. You have to do this through a content script of some kind. You can read more about it in the Chrome Developer documentation.
This code will allow you to change the text of a single selection
(tested in Chrome only)
function switchText(id) {
// Gets the selection range
// This is from Tim Down, linked below
var range, sel = window.getSelection();
if (sel.rangeCount && sel.getRangeAt) {
range = sel.getRangeAt(0);
}
// Creates a new node range
document.designMode = "on";
if (range) {
sel.removeAllRanges();
sel.addRange(range);
}
// This is from user YeppThatsMe, also linked below
document.execCommand("insertHTML", false, "<span id='own-id'>"+ document.getSelection()+"</span>");
document.designMode = "off";
// You can use either a variable or a string
var someNewText = "-- You can make this whatever you want --";
// Finds the new span and replaces the selection with your new text
document.getElementById("own-id").innerHTML=someNewText;
};
Sourced scripts
Tim's script
HTML5 inserCommand
Last Note
I didn't spend too long testing, and the script as-is will only change one selection per page. You'll need to tweak the way the function gets the tag and attribute info (change it to getElementsByClassName
?) to run it more than once, but this should work.