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0 pointsheavenlyblue6y ago0 comments

So what's the point of having let, then?

0 comments

let declares a block-scoped variable, while var declares a function-scoped variable.

Limiting a variable's scope can help avoid subtle and potentially annoying errors. For example, if you use a let variable inside an if block, it'll only be accessible by code inside the block. If you use var inside an if block, your variable will be visible to the entire function.

heavenlyblueOP6y ago

The truth is that if you need to declare a variable outside your current scope you should probably declare it in the outside scope in the first place.

In the scenario with var/let I need to grok the code in order to tell which variables are visible in my current scope.

jarekkruk6y ago

I tend to mainly use const, let only when necessary. I never use var and set linter to scream about it at me. IE11 supports it, so unless you develop application for IE compatibility mode (my condolences) I don't see a reason to use var. On the other hand var mainly bites you when declaring closures inside loops, also hoisting is just plain weird.

z3t46y ago

I find hoisting a convenient feature as I can declare the variable in context to where it's used. It means I do not have to break the flow of how the code reads, making the code easier to understand and less bug prone. Example:

    if(something) var foo = 1;

1 more reply

z3t46y ago

let also does some magic in for-loops, creating a new variable for each iteration, basically creating a closure.

It also throws and error if it's used before it's declared.

Let basically fix some minor issues that hard-bitten JavaScript developers have learned to avoid.

chrisweekly6y ago

block scope

j / k navigate · click thread line to collapse

0 comments

rpeden6y ago

let declares a block-scoped variable, while var declares a function-scoped variable.

heavenlyblueOP6y ago

The truth is that if you need to declare a variable outside your current scope you should probably declare it in the outside scope in the first place.

In the scenario with var/let I need to grok the code in order to tell which variables are visible in my current scope.

jarekkruk6y ago

z3t46y ago

    if(something) var foo = 1;

1 more reply

z3t46y ago

let also does some magic in for-loops, creating a new variable for each iteration, basically creating a closure.

It also throws and error if it's used before it's declared.

Let basically fix some minor issues that hard-bitten JavaScript developers have learned to avoid.

chrisweekly6y ago

block scope

j / k navigate · click thread line to collapse