Use PROMPT_COMMAND and nvm to auto-switch versions of node

nvm_auto_switching.sh

#!/bin/bash

# Activate a version of Node that is read from a text file via NVM
function use_node_version()
{
  local TEXT_FILE_NAME="$1"
  local CURRENT_VERSION=$([ -n "$HAS_NVM" ] && nvm current)
  local PROJECT_VERSION=$([ -n "$HAS_NVM" ] && nvm version $(cat "$TEXT_FILE_NAME"))

  # If the project file version is different than the current version
  if [ "$CURRENT_VERSION" != "$PROJECT_VERSION" ]
  then
    [ -n "$HAS_NVM" ] && nvm use "$PROJECT_VERSION"
  fi
}

# Read the .nvmrc and switch nvm versions if exists upon dir changes
function read_node_version()
{
  # Only run if we actually changed directories
  if [ "$PWD" != "$READ_NODE_VERSION_PREV_PWD" ]
	then
    export READ_NODE_VERSION_PREV_PWD="$PWD";

    # If there's an .nvmrc here
    if [ -e ".nvmrc" ]
		then
      use_node_version ".nvmrc"
      return
    fi

    # If there's a .node-version here
    if [ -e ".node-version" ]
		then
      use_node_version ".node-version"
      return
    fi
  fi
}

[[ $PROMPT_COMMAND != *"read_node_version"* ]] && export PROMPT_COMMAND="$PROMPT_COMMAND read_node_version ;"