Simplemde-markdown-editor: Get preview HTML programmatically

[IonicaBizau]

How to get the HTML which would be returned by the preview functionality?

[tommi-hirvonen]

var simplemde = new SimpleMDE(...)
simplemde.markdown(simplemde.value())

[WesCossick]

simplemde.options.previewRender("This is *example* Markdown");

[cory-haser]

FUTURE USERS: simplemde.togglePreview();