Is it necessary 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. … 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.

What happens if you don’t use VAR in JavaScript?

If you use var the variable is declared within the scope you are in (e.g. of the function). 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.

Is VAR still used in JavaScript 2020?

With var it’s still possible as JS when it compiles all scripts it stack declaration of all variables to the very top of the global script, and only assigns value when script triggers the block of code where variable is declared.

Should I stop using var in JavaScript?

Yes, if you decided to don’t support older browser or if you are using a transpiler. In ES6, there’s no any reason to prefer var in place of let or const . The only useful application of var is that a global can be redefined in global scope multiple times without causing an error.

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When should you use VAR in 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.

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.

Why do people still use VAR in JavaScript?

It’s because old JavaScript does not have block scope. So x defined inside for loop is accessible outside the brackets. So to introduce block scope we will replace all var with let.

Can we declare variable without var in Javascript?

Variables can be declared and initialize without the var keyword. However, a value must be assigned to a variable declared without the var keyword. The variables declared without the var keyword becomes global variables, irrespective of where they are declared. Visit Variable Scope in JavaScript to learn about it.

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.