commands/install.js
function isModuleInstalledGlobally(name, fn) {
  var cmd = 'npm ls --global --json --depth=0';
  exec(cmd, function(err, stdout) {
    if (err) {
      return fn(err);
    }

    var data = JSON.parse(stdout);
    var installed = data.dependencies[name];
    fn(null, installed !== undefined);
  });
}
function isModuleInstalledGlobally(name, fn) {
  var cmd = 'npm ls --global --json --depth=0';
  exec(cmd, function(err, stdout) {
    if (err) {
      return fn(err);
    }

    var data = JSON.parse(stdout);
    var installed = data.dependencies[name];
    fn(null, installed !== undefined);
  });
}
function isModuleInstalledGlobally ( name , fn ) { var cmd = 'npm ls --global --json --depth=0' ; exec ( cmd , function ( err , stdout ) { if ( err ) { return fn ( err ) ; } var data = JSON . parse ( stdout ) ; var installed = data . dependencies [ name ] ; fn ( null , installed !== undefined ) ; } ) ; }
Check if a module with `name` is installed globally.

@param {String} name of the module, e.g. jshint
@param {Function} fn (error, exists)
Check if a module with name is installed globally .