This is why TypeScript (and ES6) introduces the let keyword to allow you to define variables with true block scope. That is if you use let instead of var you get a true unique element disconnected from what you might have defined outside the scope.
Why do we use let in typescript?
When a variable is declared using let , it uses what some call lexical-scoping or block-scoping. Unlike variables declared with var whose scopes leak out to their containing function, block-scoped variables are not visible outside of their nearest containing block or for -loop.
Is Let better than VAR?
If you are using ES6+ syntax then no, not really. 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.
What is difference between LET and const in typescript?
Turns out, const is almost exactly the same as let . However, the only difference is that once you’ve assigned a value to a variable using const , you can’t reassign it to a new value. … The take away above is that variables declared with let can be re-assigned, but variables declared with const can’t be.
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.
Can I use let in TypeScript?
What is === in TypeScript?
== : When comparing primitive values, like numbers and strings, this operator will apply a type conversion before doing the comparison. 1 == “1” evaluates to true . === : This operator does not do type conversions. If the types don’t match it will always return false .
Is VAR faster than let?
In terms of performance comparison, var is faster and let is slower inside the loops while running or executing the code. Re-declaring var declared a variable in the same function or scope gives rise to Syntax Error whereas let declared variable cannot be redeclared.
Why we should not use VAR?
Does let get hoisted?
Technically, var , let and const are hoisted. var is declared and initialized during hoisting. let and const are only declared during hoisting, not initialized. Accessing uninitialized variables result in ReferenceError .
Why is let better than VAR?
let allows you to declare variables that are limited in scope to the block, statement, or expression on which it is used. This is unlike the var keyword, which defines a variable globally, or locally to an entire function regardless of block scope.
Should I use let or const?
3 Answers. Basically, use let if the variable’s value will change during the code. use const if it won‘t and you / your team want to use const in those situations in the project you’re working on; it’s a matter of style.