Example Node JS script to process SFDX deployment report output and reformat.

deploy_format_output.js

#!/usr/local/bin/node

var fs=require('fs');
var child_process=require('child_process');

var username='keir.bowden@sfdx.deploy';

var deployParams=['force:mdapi:deploy', '-d', 'src',
		  '-u', username, '--json'];

var result=execHandleError('sfdx', deployParams);
var status=result.result.status;
while (-1==(['Succeeded', 'Canceled', 'Failed'].indexOf(status))) {
	var msg='Deployment ' + status;
	if ('Queued'!=status) {
		msg+=' (' + result.result.numberComponentsDeployed + '/' +
                            result.result.numberComponentsTotal + ')'
	}
	console.log(msg);
	var reportParams=['force:mdapi:deploy:report', '-i', result.result.id,
			  '-u', username, '--json'];
	var result=execHandleError('sfdx', reportParams);
	status=result.result.status;
}

console.log('Deployment ' + result.result.status);
if ('Failed'===result.result.status) {
	if (result.result.details.componentFailures) {
		// handle if single or array of failures
		var failureDetails;
		if (Array.isArray(result.result.details.componentFailures)) {
			failureDetails=result.result.details.componentFailures;
		}
		else {
			failureDetails=[];
			failureDetails.push(result.result.details.componentFailures);
		}
		for (var idx=0; idx<failureDetails.length; idx++) {
			var failure=failureDetails[idx];
			console.log('Error: ' + failure.fileName +
						': Line ' + failure.lineNumber +
						', col ' + failure.columnNumber +
						' : '+ failure.problem);
		}
	}
}

function execHandleError(cmd, params) {
    try {
        var err=fs.openSync('/tmp/err.log', 'w');
        resultJSON=child_process.execFileSync(cmd, params, {stdio: ['pipe', 'pipe', err]});
        result=JSON.parse(resultJSON);
        fs.closeSync(err);
    }
    catch (e) {
        fs.closeSync(err);
        // the command returned non-zero - this may mean the metadata operation
        // failed, or there was an unrecoverable error
        // Is there an opening brace?
        var errMsg=''+fs.readFileSync('/tmp/err.log');
        var bracePos=errMsg.indexOf('{');
        if (-1!=bracePos) {
            resultJSON=errMsg.substring(bracePos);
            result=JSON.parse(resultJSON);
        }
        else {
            throw e;
        }
    }

    return result;
}