CodePudding user response:

InsertBefore, print ul out look

CodePudding user response:

Look from your page you didn't write ul, but you have to get the text contained in the ul element, get should be a null , print and see

CodePudding user response:

Always read the property 'insertBefore of null

Means that you want to use the insertBefore this method of object is empty, can not use the

Is ul without access to the document. QuerySelector (' ul ') didn't take into things