How to fix the error: $ is not defined?

Create an app for node, in this case:
fs.readdir('./commands/', (err, files) =>{
if(err){console.log(err)};
 let jsfile = files.filter(f => f.split('.').pop() === 'js');
 if(jsfile.length <= '0'){console.log('could not find target')};
 files.forEach((f, i) =>{
 var props = require('./commands/${f}');
 console.log('${f} loaded!')
 bot.commands.set(props.help.name, props); /* part discrord.js library 
it is not necessary to pay attention to. */
})
})

After starting the console displays an error:
Error: $ is not defined
What is my mistake?
A screenshot of the editor is attached in the comments.
March 23rd 20 at 19:05
2 answers
March 23rd 20 at 19:07
Solution
require(`./commands/${f}`);

Template strings
March 23rd 20 at 19:09
You can use the basic version output:
require('./commands/'+f);

console.log(f+"loaded!");

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