Update:
As of Notepad++ v7.6, use Plugin Admin to install JSTool per this answer
INSTALL
Download it from http://sourceforge.net/projects/jsminnpp/ and copy JSMinNpp.dll to plugin directory of Notepad++. Or you can just install “JSTool” from Plugin Manager in Notepad++.
New Notepad++ install and where did PluginManager go? See How to view Plugin Manager in Notepad++
{ "menu" : { "id" : "file", "value" : "File", "popup" : { "menuitem" : [{ "value" : "New", "onclick" : "CreateNewDoc()" }, { "value" : "Open", "onclick" : "OpenDoc()" }, { "value" : "Close", "onclick" : "CloseDoc()" } ] } } }

Tip: Select the code you want to reformat, then Plugins | JSTool | JSFormat.