Get the top and left coordinates of the caret in a <textarea> or <input type="text">, in pixels. Useful for textarea autocompletes like GitHub or Twitter, or for single-line autocompletes like the name drop-down in Twitter or Facebook's search or the company dropdown on Google Finance. How it's done: a faux <div> is created off-screen and styled exactly like the textarea or input. Then, the text of the element up to the caret is copied into the div and a <span> is inserted right after it. Then, the text content of the span is set to the remainder of the text in the <textarea>, in order to faithfully reproduce the wrapping in the faux div (because wrapping can push the currently typed word onto the next line). The same is done for the input to simplify the code, though it makes no difference. Finally, the span's offset within the textarea or input is returned.