- Why you should not use VAR?
- Is Let better than VAR?
- Is let faster than VAR?
- Is Let hoisted?
- Does IE support let?
- Is var a bad practice?
- Should I use var or const?
- Can var be Redeclared?
- What is the purpose of using VAR?
- What is the most significant difference between Let & VAR?
Why you should not use 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..
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 Let better than VAR?
The let and const declarations provide better scope management than the traditional var. Plus the var keyword may confuse programmers coming from other languages like VB or Java that use var to declare variables, but with different rules.
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?
Does IE support 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.
Should I use var or const?
var variables can be updated and re-declared within its scope; let variables can be updated but not re-declared; const variables can neither be updated nor re-declared. … While var and let can be declared without being initialized, const must be initialized during declaration.
Can var be Redeclared?
var was the way to declare variables before ES6. It can be redeclared and reassigned.
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.
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
What is the most significant difference between Let & VAR?
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.