Building Applications with Spring 5 and Vue.js 2

Block scoping, let, and const

As mentioned earlier, in ES6, you can use let to define variables or use const to define constants, and they will have block-level scope. And in the same scope, you can not redefine a variable using let. Also, you cannot access a variable or a constant that is defined with let or const before its declaration, since there is no variable hoisting with let or const.

Let's see the following workout example:

1.  function workout() {2.    let gym = 'Gym A';3. 4.    const gymStatuses = {'Gym A': 'open', 'Gym B': 'closed'};5.    for (let gym in gymStatuses) {6.      console.log(gym + ' is ' + gymStatuses[gym]);7.    }8.9.    {10.     const gym = 'Gym B';11.     console.log('Workout in ' + gym);12.     // The following will throw TypeError13.     // ...