TSLint : variable name must be in camelcase or uppercase

You can solve the problem by editing your tslint.json and adding "allow-leading-underscore" to the "variable-name" array of your "rules".

// tslint.json contents
{
  // ...
  "rules": {
    // ...
    "variable-name": [
      true,
      // ...
      "allow-leading-underscore"
    ]
  },
  // ...
}

I have updated tslint.json, configured the file and added optional arguments to the array of variable-name.

"allow-leading-underscore" allows underscores at the beginning (only has an effect if “check-format” specified)

"allow-pascal-case" allows PascalCase in addition to lowerCamelCase.

"allow-snake-case" allows snake_case in addition to lowerCamelCase.

"allow-trailing-underscore" allows underscores at the end. (only has an effect if “check-format” specified)

{
  // ...
  "rules": {
    "variable-name": [
      true,
      "allow-leading-underscore"
    ],
  },
  // ...
}

You can configure tslint.json according to your requirements.

This link might be helpful. https://palantir.github.io/tslint/rules/variable-name/