A Refresh of my emacs config using native emacs packages instead of el-get.
Uses js2-mode, flycheck and tern.
You need to npm instal -g tern in order to use that for completion.
Uses flycheck and racer. You need to use cargo to install racer somewhere on your path, and also have a source checkout of rust pointed to by the RUST_SRC_PATH environment variable to get smart completion.