Technically, var , let and const are hoisted. var is declared and initialized during hoisting. let and const are only declared during hoisting, not initialized. Accessing uninitialized variables result in ReferenceError .
Does let and const are hoisted?
let and const hoisting
Variables declared with let and const are also hoisted but, unlike var , are not initialized with a default value. An exception will be thrown if a variable declared with let or const is read before it is initialized.
Where are let variables hoisted?
Variables defined with let and const are hoisted to the top of the block, but not initialized. Meaning: The block of code is aware of the variable, but it cannot be used until it has been declared. Using a let variable before it is declared will result in a ReferenceError .
Can let be hoisted in JS?
Can I use const and let?
`const` is a signal that the identifier won’t be reassigned. `let` is a signal that the variable may be reassigned, such as a counter in a loop, or a value swap in an algorithm. It also signals that the variable will be used only in the block it’s defined in, which is not always the entire containing function.
Why is let not hoisted?
Technically, var , let and const are hoisted. … let and const are only declared during hoisting, not initialized. Accessing uninitialized variables result in ReferenceError . Prefer let over var , wherever possible to avoid the confusion arising due to hoisting.
How can I avoid variable hoisting?
Some ways to avoid hoisting are:
- Use let or const — As explained above, using let or const instead of var would throw an exception and not let the program run, hence helping catch the issue earlier.
- Use function expressions instead of function declarations.
Are function declarations hoisted?
Are let declarations hoisted?
The formal function declarations are hoisted and initialized with their function reference. let and const variables are hoisted too but they cannot be accessed before their declarations. This is called Temporal Dead Zone.
Are arrow functions hoisted?
Like traditional function expressions, arrow functions are not hoisted, and so you cannot call them before you declare them. They are also always anonymous—there is no way to name an arrow function.
Does const work in IE11?
const is fully supported in IE11 according to caniuse.com/#feat=const.
Summary. As a general rule, you should always declare variables with const, if you realize that the value of the variable needs to change, go back and change it to let. Use let when you know that the value of a variable will change. Use const for every other variable.