Recursively sort all layers in Illustrator alphabetically

sortLayers.jsx

var deep = true, // Set to false if you don't want to recursively sort layers within layers too
    isLowerFirst = true; // Set it to false if you want to place the layers with the first uppercase letter above

// Convert ILST collection into standard Array so we can use Array methods
function get(type, parent) {
    if (arguments.length == 1 || !parent) parent = app.activeDocument;
    var result = [];
    if (!parent[type]) return result;
    for (var i = 0; i < parent[type].length; i++) result.push(parent[type][i]);
    return result;
}

// Polyfill for Array.forEach
Array.prototype.forEach = function (callback) {
    for (var i = 0; i < this.length; i++) callback(this[i], i, this);
};

function sortLayersInside(parent) {
    function isUpperCase(text) {
        return /[A-Z]/.test(text.charAt(0))
    }
    function isLowerCase(text) {
        return /[a-z]/.test(text.charAt(0))
    }
    function hasMixedCase(a, b) {
        if (a.charAt(0).toLowerCase() !== b.charAt(0).toLowerCase()) return false;
        return isUpperCase(a) && isLowerCase(b) ? true : isLowerCase(a) && isUpperCase(b);
    }
    function handleMixedCase(a, b) {
        var result = a === b ? 0 : isUpperCase(a) ? 1 : -1;
        return isLowerFirst ? result : result * -1;
    }
    get("layers", parent)
        .sort(function (a, b) {
            return hasMixedCase(a.name, b.name) ?
                handleMixedCase(a.name, b.name) :
                a.name.toLowerCase().localeCompare(b.name.toLowerCase())
        })
        .forEach(function (layer) {
            layer.zOrder(ZOrderMethod.SENDTOBACK);
            if (layer.layers && layer.layers.length && deep) sortLayersInside(layer);
        });
}
sortLayersInside();

Good point. Are we certain that the ESTK String.localeCompare accurately handles other locales given that it doesn't seem to support the option parameter? I wouldn't be against the primitive comparison at all but if it doesn't accurately handle locales to begin with, we may have more luck finding some kind of polyfill to address them.

Just a quick cursory check for polyfills doesn't turn out much, I've only found one but it only supports a very small list and looking at the issues, seems to not handle accent characters well.

...Though you can always look at the source code for prototype methods in V8 directly. I'm not sure that this necessarily helps though V8 code tends to have pretty detailed explanations and a walkthrough of what the code is doing via comments.

I manually look at the result of sorting mixed alphabets with .localeCompare() and .toUpperCase(). I didn't check Chinese characters, because I don't know the correct order =)