在日常的前端开发或者 Node.js 相关项目操作中，许多小伙伴都会遇到需要切换不同 Node 版本的情况。列如有的老项目依赖较低版本的 Node，而新开发的项目又需要最新版本的 Node 支持，来回卸载安装不同版本的 Node 不仅麻烦，还容易出现各种环境问题。这时候，一款好用的 Node 版本管理工具就显得尤为重大，而nvm就是其中的佼佼者。今天就给大家带来一份超详细的 Mac 电脑安装 nvm 的教程，从基础介绍到安装前的准备工作，一步步带你搞定，即使是技术小白也能轻松上手。

一、先搞懂：nvm 到底是什么？

可能还有不少刚接触 Node 生态的小伙伴对 nvm 比较陌生，先给大家简单科普一下。nvm 全称是 Node Version Manager，顾名思义，它是一款专门用于管理 Node.js 版本的命令行工具。

有了 nvm，我们不需要再手动去官网下载不同版本的 Node 安装包，也不用由于切换版本而反复卸载旧版本。只需要在终端输入简单的命令，就能快速完成 Node 版本的安装、切换、查看和卸载等操作。列如想从 Node 16 切换到 Node 18，只需要一条命令就能实现，极大地提升了开发效率，避免了因版本不兼容带来的各种麻烦。

二、安装 nvm 前必做：卸载全局已安装的 Node

许多小伙伴在安装 nvm 之前，可能已经通过官网安装包、Homebrew 等方式在 Mac 上全局安装过 Node 了。如果不先卸载掉全局的 Node，后续安装 nvm 后可能会出现版本冲突、命令无法正常使用等问题。所以这一步超级关键，必定要仔细操作。

第一，我们需要通过终端命令查看当前 Mac 上是否存在全局安装的 Node 以及相关模块，然后逐步删除。下面是具体的操作步骤：

步骤 1：查看全局已安装的 Node 模块

打开 Mac 的「终端」（可以通过 Spotlight 搜索 “终端” 快速打开），输入以下命令，查看当前全局安装的 Node 模块列表：

npm ls -g --depth=0

执行命令后，终端会列出所有全局安装的 Node 模块（列如 npm、yarn、vue-cli 等）。记住这些模块，后续如果需要，还可以在安装好对应 Node 版本后重新安装。

步骤 2：删除全局 Node 模块目录

全局 Node 模块默认存放在
/usr/local/lib/node_modules 目录下，我们需要通过以下命令删除这个目录（由于涉及系统目录，需要输入管理员密码）：

sudo rm -rf /usr/local/lib/node_modules

输入命令后，按回车键，终端会提示输入密码（输入时密码不会显示，正常输入即可），输入密码后再次按回车，即可开始删除全局 Node 模块目录。

步骤 3：删除全局 Node 可执行文件

接下来，删除全局安装的 Node 可执行文件，输入以下命令：

sudo rm /usr/local/bin/node

同样需要输入管理员密码，确认后即可删除 Node 可执行文件。

步骤 4：删除全局 Node 模块的软链接

之前全局安装的 Node 模块（列如 npm）会在 /usr/local/bin 目录下创建软链接，这些软链接也需要一并删除，否则可能会影响后续 nvm 的使用。输入以下命令，批量删除这些软链接：

cd /usr/local/bin && ls -l | grep "../lib/node_modules/" | awk '{print $9}' | xargs sudo rm

这条命令的作用是：先进入 /usr/local/bin 目录，然后筛选出指向
/usr/local/lib/node_modules/ 目录的软链接，最后批量删除这些软链接。

步骤 5：验证是否删除成功

完成以上步骤后，我们需要验证全局 Node 是否已经成功删除。在终端输入以下两个命令：

node -v npm -v

如果终端提示 “command not found”（命令未找到），就说明全局安装的 Node 和 npm 已经成功删除了；如果依旧能显示版本号，则需要重新检查前面的步骤，确保每一步都正确执行。

到这里，安装 nvm 前的准备工作就完成了。接下来就可以正式安装 nvm 了，下一篇教程会给大家详细讲解 nvm 的具体安装步骤和使用方法，让你轻松管理各种 Node 版本，再也不用为版本切换发愁啦！

install.sh

#!/usr/bin/env bash

{ # this ensures the entire script is downloaded #

nvm_has() {
  type "$1" > /dev/null 2>&1
}

nvm_echo() {
  command printf %s
 "$*" 2>/dev/null
}

if [ -z "${BASH_VERSION}" ] || [ -n "${ZSH_VERSION}" ]; then
  # shellcheck disable=SC2016
  nvm_echo >&2 'Error: the install instructions explicitly say to pipe the install script to `bash`; please follow them'
  exit 1
fi

nvm_grep() {
  GREP_OPTIONS='' command grep "$@"
}

nvm_default_install_dir() {
  [ -z "${XDG_CONFIG_HOME-}" ] && printf %s "${HOME}/.nvm" || printf %s "${XDG_CONFIG_HOME}/nvm"
}

nvm_install_dir() {
  if [ -n "$NVM_DIR" ]; then
    printf %s "${NVM_DIR}"
  else
    nvm_default_install_dir
  fi
}

nvm_latest_version() {
  nvm_echo "v0.39.3"
}

nvm_profile_is_bash_or_zsh() {
  local TEST_PROFILE
  TEST_PROFILE="${1-}"
  case "${TEST_PROFILE-}" in
    *"/.bashrc" | *"/.bash_profile" | *"/.zshrc" | *"/.zprofile")
      return
    ;;
    *)
      return 1
    ;;
  esac
}

#
# Outputs the location to NVM depending on:
# * The availability of $NVM_SOURCE
# * The method used ("script" or "git" in the script, defaults to "git")
# NVM_SOURCE always takes precedence unless the method is "script-nvm-exec"
#
nvm_source() {
  local NVM_GITHUB_REPO
  NVM_GITHUB_REPO="${NVM_INSTALL_GITHUB_REPO:-nvm-sh/nvm}"
  local NVM_VERSION
  NVM_VERSION="${NVM_INSTALL_VERSION:-$(nvm_latest_version)}"
  local NVM_METHOD
  NVM_METHOD="$1"
  local NVM_SOURCE_URL
  NVM_SOURCE_URL="$NVM_SOURCE"
  if [ "_$NVM_METHOD" = "_script-nvm-exec" ]; then
    NVM_SOURCE_URL="https://raw.githubusercontent.com/${NVM_GITHUB_REPO}/${NVM_VERSION}/nvm-exec"
  elif [ "_$NVM_METHOD" = "_script-nvm-bash-completion" ]; then
    NVM_SOURCE_URL="https://raw.githubusercontent.com/${NVM_GITHUB_REPO}/${NVM_VERSION}/bash_completion"
  elif [ -z "$NVM_SOURCE_URL" ]; then
    if [ "_$NVM_METHOD" = "_script" ]; then
      NVM_SOURCE_URL="https://raw.githubusercontent.com/${NVM_GITHUB_REPO}/${NVM_VERSION}/nvm.sh"
    elif [ "_$NVM_METHOD" = "_git" ] || [ -z "$NVM_METHOD" ]; then
      NVM_SOURCE_URL="https://bgithub.xyz/${NVM_GITHUB_REPO}.git"
    else
      nvm_echo >&2 "Unexpected value "$NVM_METHOD" for $NVM_METHOD"
      return 1
    fi
  fi
  nvm_echo "$NVM_SOURCE_URL"
}

#
# Node.js version to install
#
nvm_node_version() {
  nvm_echo "$NODE_VERSION"
}

nvm_download() {
  if nvm_has "curl"; then
    curl --fail --compressed -q "$@"
  elif nvm_has "wget"; then
    # Emulate curl with wget
    ARGS=$(nvm_echo "$@" | command sed -e 's/--progress-bar /--progress=bar /' 
                            -e 's/--compressed //' 
                            -e 's/--fail //' 
                            -e 's/-L //' 
                            -e 's/-I /--server-response /' 
                            -e 's/-s /-q /' 
                            -e 's/-sS /-nv /' 
                            -e 's/-o /-O /' 
                            -e 's/-C - /-c /')
    # shellcheck disable=SC2086
    eval wget $ARGS
  fi
}

install_nvm_from_git() {
  local INSTALL_DIR
  INSTALL_DIR="$(nvm_install_dir)"
  local NVM_VERSION
  NVM_VERSION="${NVM_INSTALL_VERSION:-$(nvm_latest_version)}"
  if [ -n "${NVM_INSTALL_VERSION:-}" ]; then
    # Check if version is an existing ref
    if command git ls-remote "$(nvm_source "git")" "$NVM_VERSION" | nvm_grep -q "$NVM_VERSION" ; then
      :
    # Check if version is an existing changeset
    elif ! nvm_download -o /dev/null "$(nvm_source "script-nvm-exec")"; then
      nvm_echo >&2 "Failed to find '$NVM_VERSION' version."
      exit 1
    fi
  fi

  local fetch_error
  if [ -d "$INSTALL_DIR/.git" ]; then
    # Updating repo
    nvm_echo "=> nvm is already installed in $INSTALL_DIR, trying to update using git"
    command printf '
=> '
    fetch_error="Failed to update nvm with $NVM_VERSION, run 'git fetch' in $INSTALL_DIR yourself."
  else
    fetch_error="Failed to fetch origin with $NVM_VERSION. Please report this!"
    nvm_echo "=> Downloading nvm from git to '$INSTALL_DIR'"
    command printf '
=> '
    mkdir -p "${INSTALL_DIR}"
    if [ "$(ls -A "${INSTALL_DIR}")" ]; then
      # Initializing repo
      command git init "${INSTALL_DIR}" || {
        nvm_echo >&2 'Failed to initialize nvm repo. Please report this!'
        exit 2
      }
      command git --git-dir="${INSTALL_DIR}/.git" remote add origin "$(nvm_source)" 2> /dev/null 
        || command git --git-dir="${INSTALL_DIR}/.git" remote set-url origin "$(nvm_source)" || {
        nvm_echo >&2 'Failed to add remote "origin" (or set the URL). Please report this!'
        exit 2
      }
    else
      # Cloning repo
      command git clone "$(nvm_source)" --depth=1 "${INSTALL_DIR}" || {
        nvm_echo >&2 'Failed to clone nvm repo. Please report this!'
        exit 2
      }
    fi
  fi
  # Try to fetch tag
  if command git --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" fetch origin tag "$NVM_VERSION" --depth=1 2>/dev/null; then
    :
  # Fetch given version
  elif ! command git --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" fetch origin "$NVM_VERSION" --depth=1; then
    nvm_echo >&2 "$fetch_error"
    exit 1
  fi
  command git -c advice.detachedHead=false --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" checkout -f --quiet FETCH_HEAD || {
    nvm_echo >&2 "Failed to checkout the given version $NVM_VERSION. Please report this!"
    exit 2
  }
  if [ -n "$(command git --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" show-ref refs/heads/master)" ]; then
    if command git --no-pager --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" branch --quiet 2>/dev/null; then
      command git --no-pager --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" branch --quiet -D master >/dev/null 2>&1
    else
      nvm_echo >&2 "Your version of git is out of date. Please update it!"
      command git --no-pager --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" branch -D master >/dev/null 2>&1
    fi
  fi

  nvm_echo "=> Compressing and cleaning up git repository"
  if ! command git --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" reflog expire --expire=now --all; then
    nvm_echo >&2 "Your version of git is out of date. Please update it!"
  fi
  if ! command git --git-dir="$INSTALL_DIR"/.git --work-tree="$INSTALL_DIR" gc --auto --aggressive --prune=now ; then
    nvm_echo >&2 "Your version of git is out of date. Please update it!"
  fi
  return
}

#
# Automatically install Node.js
#
nvm_install_node() {
  local NODE_VERSION_LOCAL
  NODE_VERSION_LOCAL="$(nvm_node_version)"

  if [ -z "$NODE_VERSION_LOCAL" ]; then
    return 0
  fi

  nvm_echo "=> Installing Node.js version $NODE_VERSION_LOCAL"
  nvm install "$NODE_VERSION_LOCAL"
  local CURRENT_NVM_NODE

  CURRENT_NVM_NODE="$(nvm_version current)"
  if [ "$(nvm_version "$NODE_VERSION_LOCAL")" == "$CURRENT_NVM_NODE" ]; then
    nvm_echo "=> Node.js version $NODE_VERSION_LOCAL has been successfully installed"
  else
    nvm_echo >&2 "Failed to install Node.js $NODE_VERSION_LOCAL"
  fi
}

install_nvm_as_script() {
  local INSTALL_DIR
  INSTALL_DIR="$(nvm_install_dir)"
  local NVM_SOURCE_LOCAL
  NVM_SOURCE_LOCAL="$(nvm_source script)"
  local NVM_EXEC_SOURCE
  NVM_EXEC_SOURCE="$(nvm_source script-nvm-exec)"
  local NVM_BASH_COMPLETION_SOURCE
  NVM_BASH_COMPLETION_SOURCE="$(nvm_source script-nvm-bash-completion)"

  # Downloading to $INSTALL_DIR
  mkdir -p "$INSTALL_DIR"
  if [ -f "$INSTALL_DIR/nvm.sh" ]; then
    nvm_echo "=> nvm is already installed in $INSTALL_DIR, trying to update the script"
  else
    nvm_echo "=> Downloading nvm as script to '$INSTALL_DIR'"
  fi
  nvm_download -s "$NVM_SOURCE_LOCAL" -o "$INSTALL_DIR/nvm.sh" || {
    nvm_echo >&2 "Failed to download '$NVM_SOURCE_LOCAL'"
    return 1
  } &
  nvm_download -s "$NVM_EXEC_SOURCE" -o "$INSTALL_DIR/nvm-exec" || {
    nvm_echo >&2 "Failed to download '$NVM_EXEC_SOURCE'"
    return 2
  } &
  nvm_download -s "$NVM_BASH_COMPLETION_SOURCE" -o "$INSTALL_DIR/bash_completion" || {
    nvm_echo >&2 "Failed to download '$NVM_BASH_COMPLETION_SOURCE'"
    return 2
  } &
  for job in $(jobs -p | command sort)
  do
    wait "$job" || return $?
  done
  chmod a+x "$INSTALL_DIR/nvm-exec" || {
    nvm_echo >&2 "Failed to mark '$INSTALL_DIR/nvm-exec' as executable"
    return 3
  }
}

nvm_try_profile() {
  if [ -z "${1-}" ] || [ ! -f "${1}" ]; then
    return 1
  fi
  nvm_echo "${1}"
}

#
# Detect profile file if not specified as environment variable
# (eg: PROFILE=~/.myprofile)
# The echo'ed path is guaranteed to be an existing file
# Otherwise, an empty string is returned
#
nvm_detect_profile() {
  if [ "${PROFILE-}" = '/dev/null' ]; then
    # the user has specifically requested NOT to have nvm touch their profile
    return
  fi

  if [ -n "${PROFILE}" ] && [ -f "${PROFILE}" ]; then
    nvm_echo "${PROFILE}"
    return
  fi

  local DETECTED_PROFILE
  DETECTED_PROFILE=''

  if [ "${SHELL#*bash}" != "$SHELL" ]; then
    if [ -f "$HOME/.bashrc" ]; then
      DETECTED_PROFILE="$HOME/.bashrc"
    elif [ -f "$HOME/.bash_profile" ]; then
      DETECTED_PROFILE="$HOME/.bash_profile"
    fi
  elif [ "${SHELL#*zsh}" != "$SHELL" ]; then
    if [ -f "$HOME/.zshrc" ]; then
      DETECTED_PROFILE="$HOME/.zshrc"
    elif [ -f "$HOME/.zprofile" ]; then
      DETECTED_PROFILE="$HOME/.zprofile"
    fi
  fi

  if [ -z "$DETECTED_PROFILE" ]; then
    for EACH_PROFILE in ".profile" ".bashrc" ".bash_profile" ".zprofile" ".zshrc"
    do
      if DETECTED_PROFILE="$(nvm_try_profile "${HOME}/${EACH_PROFILE}")"; then
        break
      fi
    done
  fi

  if [ -n "$DETECTED_PROFILE" ]; then
    nvm_echo "$DETECTED_PROFILE"
  fi
}

#
# Check whether the user has any globally-installed npm modules in their system
# Node, and warn them if so.
#
nvm_check_global_modules() {
  local NPM_COMMAND
  NPM_COMMAND="$(command -v npm 2>/dev/null)" || return 0
  [ -n "${NVM_DIR}" ] && [ -z "${NPM_COMMAND%%"$NVM_DIR"/*}" ] && return 0

  local NPM_VERSION
  NPM_VERSION="$(npm --version)"
  NPM_VERSION="${NPM_VERSION:--1}"
  [ "${NPM_VERSION%%[!-0-9]*}" -gt 0 ] || return 0

  local NPM_GLOBAL_MODULES
  NPM_GLOBAL_MODULES="$(
    npm list -g --depth=0 |
    command sed -e '/ npm@/d' -e '/ (empty)$/d'
  )"

  local MODULE_COUNT
  MODULE_COUNT="$(
    command printf %s
 "$NPM_GLOBAL_MODULES" |
    command sed -ne '1!p' |                     # Remove the first line
    wc -l | command tr -d ' '                   # Count entries
  )"

  if [ "${MODULE_COUNT}" != '0' ]; then
    # shellcheck disable=SC2016
    nvm_echo '=> You currently have modules installed globally with `npm`. These will no'
    # shellcheck disable=SC2016
    nvm_echo '=> longer be linked to the active version of Node when you install a new node'
    # shellcheck disable=SC2016
    nvm_echo '=> with `nvm`; and they may (depending on how you construct your `$PATH`)'
    # shellcheck disable=SC2016
    nvm_echo '=> override the binaries of modules installed with `nvm`:'
    nvm_echo

    command printf %s
 "$NPM_GLOBAL_MODULES"
    nvm_echo '=> If you wish to uninstall them at a later point (or re-install them under your'
    # shellcheck disable=SC2016
    nvm_echo '=> `nvm` Nodes), you can remove them from the system Node as follows:'
    nvm_echo
    nvm_echo '     $ nvm use system'
    nvm_echo '     $ npm uninstall -g a_module'
    nvm_echo
  fi
}

nvm_do_install() {
  if [ -n "${NVM_DIR-}" ] && ! [ -d "${NVM_DIR}" ]; then
    if [ -e "${NVM_DIR}" ]; then
      nvm_echo >&2 "File "${NVM_DIR}" has the same name as installation directory."
      exit 1
    fi

    if [ "${NVM_DIR}" = "$(nvm_default_install_dir)" ]; then
      mkdir "${NVM_DIR}"
    else
      nvm_echo >&2 "You have $NVM_DIR set to "${NVM_DIR}", but that directory does not exist. Check your profile files and environment."
      exit 1
    fi
  fi
  # Disable the optional which check, https://www.shellcheck.net/wiki/SC2230
  # shellcheck disable=SC2230
  if nvm_has xcode-select && [ "$(xcode-select -p >/dev/null 2>/dev/null ; echo $?)" = '2' ] && [ "$(which git)" = '/usr/bin/git' ] && [ "$(which curl)" = '/usr/bin/curl' ]; then
    nvm_echo >&2 'You may be on a Mac, and need to install the Xcode Command Line Developer Tools.'
    # shellcheck disable=SC2016
    nvm_echo >&2 'If so, run `xcode-select --install` and try again. If not, please report this!'
    exit 1
  fi
  if [ -z "${METHOD}" ]; then
    # Autodetect install method
    if nvm_has git; then
      install_nvm_from_git
    elif nvm_has curl || nvm_has wget; then
      install_nvm_as_script
    else
      nvm_echo >&2 'You need git, curl, or wget to install nvm'
      exit 1
    fi
  elif [ "${METHOD}" = 'git' ]; then
    if ! nvm_has git; then
      nvm_echo >&2 "You need git to install nvm"
      exit 1
    fi
    install_nvm_from_git
  elif [ "${METHOD}" = 'script' ]; then
    if ! nvm_has curl && ! nvm_has wget; then
      nvm_echo >&2 "You need curl or wget to install nvm"
      exit 1
    fi
    install_nvm_as_script
  else
    nvm_echo >&2 "The environment variable $METHOD is set to "${METHOD}", which is not recognized as a valid installation method."
    exit 1
  fi

  nvm_echo

  local NVM_PROFILE
  NVM_PROFILE="$(nvm_detect_profile)"
  local PROFILE_INSTALL_DIR
  PROFILE_INSTALL_DIR="$(nvm_install_dir | command sed "s:^$HOME:$HOME:")"

  SOURCE_STR="
export NVM_DIR="${PROFILE_INSTALL_DIR}"
[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"  # This loads nvm
"

  # shellcheck disable=SC2016
  COMPLETION_STR='[ -s "$NVM_DIR/bash_completion" ] && . "$NVM_DIR/bash_completion"  # This loads nvm bash_completion
'
  BASH_OR_ZSH=false

  if [ -z "${NVM_PROFILE-}" ] ; then
    local TRIED_PROFILE
    if [ -n "${PROFILE}" ]; then
      TRIED_PROFILE="${NVM_PROFILE} (as defined in $PROFILE), "
    fi
    nvm_echo "=> Profile not found. Tried ${TRIED_PROFILE-}~/.bashrc, ~/.bash_profile, ~/.zprofile, ~/.zshrc, and ~/.profile."
    nvm_echo "=> Create one of them and run this script again"
    nvm_echo "   OR"
    nvm_echo "=> Append the following lines to the correct file yourself:"
    command printf "${SOURCE_STR}"
    nvm_echo
  else
    if nvm_profile_is_bash_or_zsh "${NVM_PROFILE-}"; then
      BASH_OR_ZSH=true
    fi
    if ! command grep -qc '/nvm.sh' "$NVM_PROFILE"; then
      nvm_echo "=> Appending nvm source string to $NVM_PROFILE"
      command printf "${SOURCE_STR}" >> "$NVM_PROFILE"
    else
      nvm_echo "=> nvm source string already in ${NVM_PROFILE}"
    fi
    # shellcheck disable=SC2016
    if ${BASH_OR_ZSH} && ! command grep -qc '$NVM_DIR/bash_completion' "$NVM_PROFILE"; then
      nvm_echo "=> Appending bash_completion source string to $NVM_PROFILE"
      command printf "$COMPLETION_STR" >> "$NVM_PROFILE"
    else
      nvm_echo "=> bash_completion source string already in ${NVM_PROFILE}"
    fi
  fi
  if ${BASH_OR_ZSH} && [ -z "${NVM_PROFILE-}" ] ; then
    nvm_echo "=> Please also append the following lines to the if you are using bash/zsh shell:"
    command printf "${COMPLETION_STR}"
  fi

  # Source nvm
  # shellcheck source=/dev/null
  . "$(nvm_install_dir)/nvm.sh"

  nvm_check_global_modules

  nvm_install_node

  nvm_reset

  nvm_echo "=> Close and reopen your terminal to start using nvm or run the following to use it now:"
  command printf "${SOURCE_STR}"
  if ${BASH_OR_ZSH} ; then
    command printf "${COMPLETION_STR}"
  fi
}

#
# Unsets the various functions defined
# during the execution of the install script
#
nvm_reset() {
  unset -f nvm_has nvm_install_dir nvm_latest_version nvm_profile_is_bash_or_zsh 
    nvm_source nvm_node_version nvm_download install_nvm_from_git nvm_install_node 
    install_nvm_as_script nvm_try_profile nvm_detect_profile nvm_check_global_modules 
    nvm_do_install nvm_reset nvm_default_install_dir nvm_grep
}

[ "_$NVM_ENV" = "_testing" ] || nvm_do_install

} # this ensures the entire script is downloaded #