问题
It looks like selected some text, but the background color will not disappear when you click it or move cursor.
回答1:
You can't use textarea element for this. Just make a contentEditable contentEditable div and use javascript to style it.
回答2:
It may be a div with contentEditable set to true
回答3:
That could be a div the styled during events and as other suggested make it contentEditable. With regards to textarea I have read similar question here. Check it if it's what your looking for.
来源：https://stackoverflow.com/questions/5470671/how-to-set-background-color-for-some-inner-text-of-html-textarea-element