Hi,
Due to this problem, We aren't able to roll out a release to support ios9 devices.
May I know when to expect this fix to be released?

We don't have a specific date yet, but it should be very shortly, in the next couple of days, maybe a little over a week, would you agree @Akryum ?

As a workaround you should be able to add vue-cli-service to transpileDependencies I think. Can you try this?

Thanks for the suggestion. But let me clarify,
I assume you expect me to add this in package.json. right?

"transpileDependencies":{
"vue-cli-service":"^3.0.0-beta.6"
}

No, its an option in vue.config.js

See here: https://cli.vuejs.org/config/#transpiledependencies

When i include transpileDependencies in vue.config.js, I get below error:
Invalid options in vue.config.js: "transpileDependencies" is not allowed

That option didn't exist yet in beta.6, you should upgrade either way

hmm, may be, here are the dependencies

"@vue/cli-plugin-babel": "^3.0.0-beta.6",
"@vue/cli-plugin-e2e-nightwatch": "^3.0.0-beta.6",
"@vue/cli-plugin-eslint": "^3.0.0-beta.6",
"@vue/cli-plugin-unit-jest": "^3.0.0-beta.6",
"@vue/cli-service": "^3.0.0-beta.6",
"@vue/eslint-config-standard": "^3.0.0-beta.6",

After beta.6 came another 10 beta releases, and now we are on the 3rd Release Candidate.

oh ok. I will try updating them to 3rd release candidate

Updated the vue cli to version:3.0.0-rc.3

After including below in vue.config.js

transpileDependencies: ['@vue/cli-service'] or
transpileDependencies: ['vue-cli-service'],
I still see 'let' being used in setPublicPath.js under node_modules/@vue/cli-service/lib/command/build

So including transpileDependencies option on the vue-config didn't seem to work, unless I have done something wrong.
As this is top priority for us, it would be great to see any other work arounds that we could try, thanks for you support so far.

The latest version is rc.4. This PR is not in rc.3.

Thanks a lot that seemed to fix the let on the setPublicPath.js.
But I can still see a let being used on the minified version in file: dist/js/vendor.db846e77.js
let t;(t=window.document.currentScript)

I'm not aware of other code that we inject, so this could be coming from any of your project's dependencies.

Can you provide a reproduction?

You are right!
The issue is due to transitive dependencies of old Vue-cli-service versions in our package.json.
We'll work with the teams to get them updated to RC4 version of Vue-cli-service.
Thanks for the support!