I understand that a body of ASPX page published on site is stored in a dedicated column. What is exact name of this column? Some authors mention "PublishingPageContent", others "WikiField". Does it depend on library type? How to determine exact field in client side code? Thank you.
It depends on the page type being used, if it's a Publishing Page, the field name is "PublishingPageContent". If it's a Wiki page, the field name is "WikiField".
In case its a modern page in SharePoint Online, it will be "CanvasContent1"
Thanks to Gautam Sheth for mentioning this in comments