在 React.js 中使用 execCommand 时无法读取未定义的属性“contentDocument”

Question

I want to make the selected text bold on click of a button. I want to use the execCommand() function but I keep getting this error: TypeError: Cannot read property 'contentDocument' of undefined.

 import React, { useEffect } from 'react' import "./MainText.css" import "./App.css"; import FormatColorFillIcon from '@material-ui/icons/FormatColorFill'; import BorderColorIcon from '@material-ui/icons/BorderColor'; function MainText() { function enableEditMode() { const textpart = document.getElementsByName('textPart')[0]; const iframeDocument= textpart.contentDocument || textpart.contentWindow.document; iframeDocument.designMode = "on"; iframeDocument.contentEditable = true; } useEffect(() => { enableEditMode(); }, []) function execCmd(command) { const textpart = document.getElementsByName('textPart')[0]; const iframeDocument= textpart.contentDocument || textpart.contentWindow.document; iframeDocument.execCommand(command, false, null); } return ( <div className="mainText"> <button onClick={execCmd('bold')}><i class="fa fa-bold"></i></button> <div className="mainText__second"> <iframe name="textPart" frameBorder="0" ></iframe> </div> </div> )

please help in this.

Answer 1

It looks like this may be because your are assigning the result of calling the execCmd() function to the onClick property - rather than an actual function expression as is expected. In this case the execCmd('bold') expression is evaluated even before the DOM actually has a chance to be mounted.

Try something like this instead:

onClick={() => execCmd('bold')}