For future reference there is also a solution without jQuery - just have the wrapper div style contain overflow:hidden and use this JavaScript two-liner:

// get the width of the textarea minus scrollbar

var textareaWidth = document.getElementById("textarea").scrollWidth;



// width of our wrapper equals width of the inner part of the textarea

document.getElementById("wrapper").style.width = textareaWidth + "px";

Update: you can use the same principle to create scrollable div without scrollbar.