Question: Should I Use VAR Or Let?

Is var a bad practice?

var speeds up the writing, but may slow down the reading a bit.

It’s obviously not a code behaviour rule like “Always initialize variables” because the two alternatives (writing var and writing the type) have exactly the same behaviour.

So it’s not a critical rule..

What is the purpose of using VAR?

Using var lets you hide external variables that have the same name. In this way you can simulate a “private” variable, but that’s another topic. A rule of thumb is to always use var , because otherwise you run the risk of introducing subtle bugs.

What is VAR and 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 better to use let or VAR?

let is preferable to var because it reduces the scope in which an identifier is visible. It allows us to safely declare variables at the site of first use. const is preferable to let .

Should you still use VAR?

Variables declared with var are not block scoped (although they are function scoped), while with let and const they are. This is important because what’s the point of block scoping if you’re not going to use it.

What’s the difference between VAR and let?

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.

Is VAR dead?

var isn’t dead – it still does what it always has done — it’s function scoped and you can reassign or re-bind it. You may very well continue to choose it.

What can I use instead of VAR in Javascript?

Use ‘let’ and ‘const’ instead of ‘var’var uses something called ‘hoisting’, which can lead to unexpected results.let and const are both block-scoped. Which means you can declare them in for loop or if statement, and they will only be valid for that block. This helps with spotting bugs and makes your code more robust.const prevents variable re-assignment.Aug 29, 2018

Is let faster than VAR?

After testing this in Chrome and Firefox, this shows that let is faster than var , but only when inside a different scope than the main scope of a function. In the main scope, var and let are roughly identical in performance. In IE11 and MS Edge, let and var are roughly equal in performance in both cases.

Is Let hoisted?

All declarations (function, var, let, const and class) are hoisted in JavaScript, while the var declarations are initialized with undefined , but let and const declarations remain uninitialized. They will only get initialized when their lexical binding (assignment) is evaluated during runtime by the JavaScript engine.

Is VAR needed JavaScript?

2 Answers. The var keyword is never “needed”. However if you don’t use it then the variable that you are declaring will be exposed in the global scope (i.e. as a property on the window object). … Usually you only want your variable to be visible in the current scope, and this is what var does for you.

Why is const better than 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 happens if you dont use VAR in JavaScript?

If you don’t use var , the variable bubbles up through the layers of scope until it encounters a variable by the given name or the global object (window, if you are doing it in the browser), where it then attaches. … If you use var in the global scope, the variable is truly global and cannot be deleted.

Is it bad to use var in C#?

If you enter text it will be interpreted as a string, etc. ‘var’s can even hold various objects and will behave properly. As you probably already know, C# has supported the variable type var since version 3.0. Ever since, the debate has raged on: you should always use var; you should never use var.

Why you should not use VAR?

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. … They both work with block scope, which means, if variables or constants are declared inside a block, they will not be available to the “parent” blocks.

Does IE support let?

Internet Explorer browser version 11 partially supports JAVASCRIPT let and partial support for Internet Explorer refers ot supporting an older version of the web browser.

Is VAR deprecated in JavaScript?

The scope of a JavaScript variable declared with var is its current execution context. … The let statement allows you to create a variable with the scope limited to the block on which it is used. const. const statement values can be assigned once and they cannot be reassigned.

Is Javascript hoisting bad?

Variables declared using var can be accessed in the whole scope (and we already know that var has a bigger scope). You can access them before they are declared. In such case, their value would be undefined though, as only declarations and not initializations are hoisted. This is generally considered a bad practice.