code: function checkCommon(call) {
      if (call.callee.type !== 'Identifier') return
      if (call.callee.name !== 'require') return
      if (call.arguments.length !== 1) return
  
      const modulePath = call.arguments[0]
      if (modulePath.type !== 'Literal') return
      if (typeof modulePath.value !== 'string') return
  
      checkSourceValue(modulePath, call)
    }
docs: for CommonJS `require` calls adapted from @mctep: http://git.io/v4rAu