Sorry if this is very basic. I'm new to Javascript and can't seem to find an answer anywhere.

I realized while coding that I've been omitting the let keyword from my for loops. But in all the documentation I've read, I always see let included.

For example, when I use for-loops like this, they work as intended:

for (i = 0; i < 10; i  )

But everything I read says to structure loops like this:

for (let i = 0; i < 10; i  )

I've already determined that i isn't being initialized as a var by checking whether it was accessible outside the loop.

When I omit let, is the let implied and interpreted properly? Or maybe my IDE (VSCode) is catching my omission and fixing it for me? Or is this a bad practice and I need to explicitly declare index variables with let?

CodePudding user response：

In JavaScript, the let keyword is used to declare variables that are block-scoped, which means that they are only accessible within the block in which they are defined. The var keyword, on the other hand, is function-scoped, which means that it is accessible within the entire function in which it is defined.

In a for loop, the loop variable (e.g. i in your example) is traditionally declared using the let keyword to ensure that it is only accessible within the loop block. This is generally considered good practice as it helps to avoid potential issues with variable shadowing (when a variable with the same name as a block-scoped variable is defined within the same block).

However, if you omit the let keyword when declaring the loop variable, JavaScript will still interpret it correctly as a block-scoped variable. This is because the for loop syntax includes an implicit block, which means that any variables declared within the loop are automatically block-scoped.

So, in your example, omitting the let keyword will not cause any issues with your code. However, it is generally considered good practice to include the let keyword when declaring loop variables in order to make it clear that the variable is block-scoped and to avoid any potential confusion or issues with variable shadowing