node/tools/eslint/lib/rules/sort-vars.js

/**
 * @fileoverview Rule to require sorting of variables within a single Variable Declaration block
 * @author Ilya Volodin
 */

"use strict";

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = function(context) {

    var configuration = context.options[0] || {},
        ignoreCase = configuration.ignoreCase || false;

    return {
        "VariableDeclaration": function(node) {
            node.declarations.reduce(function(memo, decl) {
                var lastVariableName = memo.id.name,
                    currenVariableName = decl.id.name;

                if (ignoreCase) {
                    lastVariableName = lastVariableName.toLowerCase();
                    currenVariableName = currenVariableName.toLowerCase();
                }

                if (currenVariableName < lastVariableName) {
                    context.report(decl, "Variables within the same declaration block should be sorted alphabetically");
                    return memo;
                } else {
                    return decl;
                }
            }, node.declarations[0]);
        }
    };
};