`no-unused-vars` should not flag constants declared with `const`

What version of ESLint are you using? 2.9.0

What parser (default, Babel-ESLint, etc.) are you using? default

Please show your full configuration:

{
    "env": {
        "browser":true,
        "es6":true
    },
    "plugins": [
        "html"
    ],
    "rules": {
        "no-mixed-spaces-and-tabs":[2, true],
        "no-redeclare":2,
        "no-use-before-define":[2, "nofunc"],
        "no-unused-vars":1,
        "no-undef":2,
        "eqeqeq":2,
        "consistent-return":1,
        "radix":2,
        "console":0,
        "camelcase":0,
        "strict":0,
        "quotes":[2, "double", "avoid-escape"],
        "new-cap":0,
        "space-infix-ops":0,
        "no-console":0,
        "no-delete-var":0,
        "no-underscore-dangle":0,
        "no-multi-spaces":0,
        "dot-notation":[2, {"allowKeywords": false}],
        "space-unary-ops":1,
        "key-spacing": [1, {"beforeColon": false, "afterColon": true, "mode": "minimum"}],
        "no-empty":2,
        "brace-style": [1, "stroustrup", { "allowSingleLine": true }],
        "keyword-spacing": 2,
        "no-space-before-semi": 0,
        "space-before-function-paren": [2, "never"],
        "no-trailing-spaces": [2, { "skipBlankLines": false }],
        "prefer-const": ["error"]
    }
}

What did you do? Please include the actual source code causing the issue.

const EDGE_OFFSET = 15;

What did you expect to happen? No warnings since EDGE_OFFSET is a constant, not a variable.

What actually happened? Please include the actual, raw output from ESLint.

minimum.js
  1:7  warning  'EDGE_OFFSET' is defined but never used  no-unused-vars

✖ 1 problem (0 errors, 1 warning)

[ilyavolodin]

So you are arguing semantics of the name of the rule? Const is a read-only variable (not really completely true in JS, but that’s what it is in other languages).

[ghengeveld]

Of course I’m not familiar with your codebase and conventions, but nowadays it’s common to use const everywhere, not just for actual (global) constants. If I need a let (or var) I will rewrite my code to not need a let. In general I write all my code in an immutable fashion, so const is the only way to go. This means not just my contants (for example Redux action types) will use const, but also any other variables.

What I’m trying to say is, don’t hold on too tight to your ALL_CAPS convention. It generally doesn’t help readability if your code is sprinkled with all caps.