Quick Answer: Var Ou Let Javascript?

Is let same as VAR in Javascript?

let allows you to declare variables that are limited to the scope of a block statement, or expression on which it is used, unlike the var keyword, which declares a variable globally, or locally to an entire function regardless of block scope.

Which is better VAR or let in Javascript?

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.

Is it bad to use VAR in Javascript?

In Javascript, it doesn’t matter how many times you use the keyword “var”. If it’s the same name in the same function, you are pointing to the same variable. This function scope can be a source of a lot of bugs.

Is VAR deprecated in Javascript?

There is nothing really to gain by removing var from the language. For languages like HTML and Javascript that are interpreted – backward compatability is absolutely mandatory. If var was changed to behave like let then the console. log would cause a reference error because of the scope difference.

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Is Let better than VAR?

The main difference is the scope difference, while let can be only available inside the scope it’s declared, like in for loop, var can be accessed outside the loop for example. From the documentation in MDN (examples also from MDN):

Should I use VAR or let?

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.

What will happen if an infinite while loop is run in JavaScript?

What are infinite loops? An infinite loop is a piece of code that keeps running forever as the terminating condition is never reached. An infinite loop can crash your program or browser and freeze your computer.

What’s the difference between VAR and let Swift?

Both let and var are for creating variables in Swift. let helps you create immutable variables (constants) while on the other hand var creates mutable variables. The difference between them is that when you create a constant using let you have to assign something to it before the first use and can’t reassign it.

What is == and === in JavaScript?

= is used for assigning values to a variable in JavaScript. == is used for comparison between two variables irrespective of the datatype of variable. === is used for comparision between two variables but this will check strict type, which means it will check datatype and compare two values.

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Should you ever use var Javascript?

Most Javascript experts agree var shouldn’t be used. Douglas Crockford, the man who popularized JSON, is against the use of var. He indicates that, “var might possibly still be useful in an extreme case like machine-generated code, but I’m stretching hard there.

Why you should stop using var?

Closures. This one’s hard to understand if it’s a new concept, but a closure is a function that references a free variable. When we have a closure with a var variable, the reference is remembered, which can be troublesome when inside a loop where that variable changes.

When should you use VAR Javascript?

When you use var, you are instantiating a variable in the current scope. This will also prevent access of variables named the same in higher scope, within the current scope.

What does VAR do in JavaScript?

3 Answers. Basically, var declares a variable and you can also assign to it at the same time. Without var, it’s assigning to the variable. Assigning will either assign to an existing variable or create a global variable of that name then assign to it.

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