Node.js NPM 无法替换配置中的 env：${NPM_TOKEN}

我正在try 构建react应用程序，但当我执行命令npm -i时，它会给我以下错误:

Error: Failed to replace env in config: ${NPM_TOKEN}
    at /usr/local/lib/node_modules/npm/lib/config/core.js:415:13
    at String.replace (<anonymous>)
    at envReplace (/usr/local/lib/node_modules/npm/lib/config/core.js:411:12)
    at parseField (/usr/local/lib/node_modules/npm/lib/config/core.js:389:7)
    at /usr/local/lib/node_modules/npm/lib/config/core.js:330:24
    at Array.forEach (<anonymous>)
    at Conf.add (/usr/local/lib/node_modules/npm/lib/config/core.js:328:23)
    at ConfigChain.addString (/usr/local/lib/node_modules/npm/node_modules/config-chain/index.js:244:8)
    at Conf.<anonymous> (/usr/local/lib/node_modules/npm/lib/config/core.js:316:10)
    at /usr/local/lib/node_modules/npm/node_modules/graceful-fs/graceful-fs.js:78:16
/usr/local/lib/node_modules/npm/lib/npm.js:61
      throw new Error('npm.load() required')
      ^

Error: npm.load() required
    at Object.get (/usr/local/lib/node_modules/npm/lib/npm.js:61:13)
    at process.errorHandler (/usr/local/lib/node_modules/npm/lib/utils/error-handler.js:205:18)
    at process.emit (events.js:182:13)
    at process._fatalException (internal/bootstrap/node.js:448:27)

我用的是MacOS High Sierra.我try 使用以下命令将NPM_令牌设置为环境变量:

set -x NPM_TOKEN = xyz

但它不起作用.