You can use double slash //for single line of code
//console.log("Hello world!")
If you want to comment out multiple lines of code here is the two ways.
First: everything between /**/
/*
console.log("Hello world1!")
console.log("Hello world2!")
console.log("Hello world3!")
*/
Second: select all lines, which you want to comment out and use:
ctrl+k+c //to comment out
ctrl+k+u //to uncomment
//console.log("Hello world1!")
//console.log("Hello world2!")
//console.log("Hello world3!")