Typescript - Type changes to string in for loop for array

Question

I have declared a for loop on an array of a specific type. When I use this array in for loop, I get error because typescript detects it as type of string rather than the type of specific item as declared.

const repos: Repo[] = config.get("repos");
for(const repo in repos) {
  calculate(repo)
}

I get error that the value that I am passing to calculate is not of type Repo, but of type string.

NOTE: This is not a runtime error. I get it when in VS Code with code ts(2345)

Nicholas Tower · Accepted Answer · 2020-06-21 06:03:52Z

6

You likely meant to use a for ... of loop, not a for ... in loop. The code you've written loops over the enumerable keys of an object, so repo will start off as the string "0", then "1", etc. If instead you do for ... of, you'll iterate through the array with repo being assigned the values in the array.

for(const repo of repos) {
  calculate(repo)
}

answered Jun 21, 2020 at 6:03

Nicholas Tower

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