node.js how to check a process is running by the process name?

You can use the ps-node package.

https://www.npmjs.com/package/ps-node

var ps = require('ps-node');

// A simple pid lookup 
ps.lookup({
    command: 'node',
    psargs: 'ux'
    }, function(err, resultList ) {
    if (err) {
        throw new Error( err );
    }

    resultList.forEach(function( process ){
        if( process ){
            console.log( 'PID: %s, COMMAND: %s, ARGUMENTS: %s', process.pid, process.command, process.arguments );
        }
    });
});

I believe you’ll be looking at this example. Check out the site, they have plenty of other usages. Give it a try.

Just incase you are not bound to nodejs, from linux command line you can also do ps -ef | grep "YOUR_PROCESS_NAME_e.g._nodejs" to check for a running process.