10

http://blog.grossman.io/how-to-write-async-await-without-try-catch-blocks-in-javascript/ In this link, there are some codes that access to a variable in try catch but when I try this in my server It doesn't work because It's out of scope. how can I do this?

try {
  const foo = "bar"
} catch (e) {
  console.log(e)
}

try {
  console.log(foo) -> is not defined
} catch (e) {
  console.log(e)
}
Phillip YS
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1 Answers1

25

The author of that post clearly did a mistake there––it happens to all of us.

So, the const declarations are block-scoped, like the docs say:

Constants are block-scoped, much like variables defined using the let statement. The value of a constant cannot change through re-assignment, and it can't be redeclared.

That's why you cannot access it outside of the try-catch block.

To solve the problem:

  • Either use var instead of const:

    try {
  // When declared via `var`, the variable will
  // be declared outside of the block
  var foo = "bar"
} catch (e) {
  console.log(e)
}

try {
  console.log(foo)
} catch (e) {
  console.log(e)
}

  • Or you can declare the variable outside of the try-catch, using let:

    // Maybe it's clearer to declare it with let and 
// assign the value in the first try-catch
let foo;
try {
  foo = "bar"
} catch (e) {
   console.log(e)
}

try {
  console.log(foo)
} catch (e) {
  console.log(e)
}
Ionică Bizău
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