@lunaticmuch/front-matter-manipulator/lib/util/convertToArray.js

A utility for parsing and manipulating documents with Front Matter

export default function convertToArray(obj, key) {
    key = key.split('.');

    var i = 0;
    var parent = obj;
    for (i = 0; i < key.length - 1; i++)
        parent = obj;
    obj = obj[key[i]];

    if (key.length > 1) {
        convert(i, obj, parent, key);
    } else {
        convert(i, parent, {}, key);
    }
}

function convert(index, obj, parentObj, key) {
    if (!Array.isArray(obj) && !Array.isArray(parentObj) && !Array.isArray(obj[key[index]])) {
        var value = obj[key[index]];
        var newValue = [value];

        delete obj[key[index]];
        obj[key[index]] = newValue;
    }
}