Should I use var or const?

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. Do not use var.

Is VAR faster than const?

Comparing const to compiling The reason const is not faster than var is that const is not really a new feature, as JavaScript of course had variables all along. A minor change in lexical scope really doesn’t affect anything regarding performance, even with hoisting (or the lack there-of).

What is difference between 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.

What is difference between VAR and let?

var and let are both used for variable declaration in javascript but the difference between them is that var is function scoped and let is block scoped. It can be said that a variable declared with var is defined throughout the program as compared to let.

What is var used for in JavaScript?

The var statement declares a variable. Variables are containers for storing information. Creating a variable in JavaScript is called “declaring” a variable: var carName; After the declaration, the variable is empty (it has no value).

Is const faster?

No, const does not help the compiler make faster code. Const is for const-correctness, not optimizations.

What is the difference between undefined and null?

Many times we often get confused on what the difference between UNDEFINED and NULL is. Here as the variable is declared but not assigned to any value, the variable by default is assigned a value of undefined. On the other hand, null is an object. It can be assigned to a variable as a representation of no value.

What is difference between VAR and let in angular?

The main difference between let and var is that scope of a variable defined with let is limited to the block in which it is declared while variable declared with var has the global scope. So we can say that var is rather a keyword which defines a variable globally regardless of block scope.