overleaf solves the problem of Elsvier template elsarticle, the reference number does not display [1-4], solves the problem of "option clash for package natbib" in the elsarticle template

Since Elsvier has imported \usepackage{natbib} by default

So put two lines in the import package

\setcitestyle{square,numbers,sort&compress}
\biboptions{numbers,sort&compress}

square means square brackets, sort&compress means sorting and compressing.