test: refactoring test-pipe-head

- Updated assert.equal to assert.strictEqual
- Updated 'var' to 'const'
- Using template literals
PR-URL: #10036
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Italo A. Casas <me@italoacasas.com>

Author: furnox

test/parallel/test-pipe-head.js

@@ -1,17 +1,17 @@
 'use strict';
-varcommon=require('../common');
-varassert=require('assert');
+constcommon=require('../common');
+constassert=require('assert');
 
-varexec=require('child_process').exec;
-varjoin=require('path').join;
+constexec=require('child_process').exec;
+constjoin=require('path').join;
 
-varnodePath=process.argv[0];
-varscript=join(common.fixturesDir,'print-10-lines.js');
+constnodePath=process.argv[0];
+constscript=join(common.fixturesDir,'print-10-lines.js');
 
-varcmd='"'+nodePath+'" "'+script+'" | head -2';
+constcmd=`"${nodePath}" "${script}" | head -2`;
 
 exec(cmd,common.mustCall(function(err,stdout,stderr){
-if(err)throwerr;
-varlines=stdout.split('\n');
-assert.equal(3,lines.length);
+assert.ifError(err);
+constlines=stdout.split('\n');
+assert.strictEqual(3,lines.length);
 }));