Here's another way to verify that let and const variables do get hoisted.

If we run the below code in Chrome console, we can see that under the scripts tab, only y will be present:

debugger;
console.log(x) 
console.log(y)  
let y = 10;

Script
y: undefined

If there were no hoisting happening with let, it should have "seen" y also.

If we run the same code in FireFox console, the message is even clearer—it says y is uninitialized (as opposed to y is undefined if we had used var instead of let. Also note that it shows under the Block tab, as opposed to Scripts tab in Chrome, making it clear that it's a block-scoped variable.

Block
​y: (uninitialized)

The above makes it clear that both var and let/const variables are hoisted but var variables are initilaized with undefined whereas let/const variables are uninitialized (not given any value at all—even undefined—until execution reaches the "declaration*" line.