I want to design form, for SharePoint library.

Previously I had deign complex InfoPath form, But now I don't want to use InfoPath form.

Since Microsoft announced in a blog post titled Update on InfoPath and SharePoint Forms that InfoPath 2013 will be supported in SharePoint 2016 and within Office 365 until further notice, So what is best tools to use for form development for SharePoint.

Basically I'm looking alternative for InfoPath forms.

Please suggest some alternatives.