Think ES5 and ES6 language features are pretty confusing. I got mixed up with ES2015 with ES5, thinking "let or destructuring" feature were actually supported. What a huge mixed up.
What was actually supported by ES5 is pretty minimal. ES6 is a huge change.
You can easily find out the list of features ES5, ES6 supports by clicking on this link here.
To learn about ES6 or ES2015, please click here. Think i just got confused again.