Recursing through a nested block data structure (code simplified for discussion)

data

[
    {
        "indentLevel": 0,
        "selector": "body",
        "declarations": [
            "    margin: auto",
            "    width: 1000px"
        ],
        "children": []
    },
    {
        "indentLevel": 0,
        "selector": "#divID",
        "declarations": [
            "    font: 12px Helvetica, Arial, sans-serif",
            "    color: green",
            "    background: yellow"
        ],
        "children": [
            {
                "indentLevel": 1,
                "selector": ".className",
                "declarations": [
                    "    color: blue",
                    "    width: 500px"
                ],
                "children": []
            }
        ]
    }
]

first-attempt-recursion

var holder = [];

var cssFormat = function cssFormat (tree, prefix) {

	prefix = prefix || "";


	return tree.map(function(elem, i){
		var beginBlock = " {" + "\n",
			endBlock = "\n" + "}",
			sel = prefix + elem.selector,
			dec = elem.declarations.join("; \n") + ";",
			block,
			children = "",
			parents;

		block = sel + beginBlock + dec + endBlock;

		holder.push(JSON.stringify(block, undefined, 2));

		if (elem.children.length) {
			children = cssFormat(elem.children, sel);
		}

		return block;

	});
};

second-attempt-recursion

var blockToCSS = function blockToCSS(block) {
	var beginBlock = " {" + "\n",
		endBlock = "\n" + "}",
		output = [],
		sel,
		dec,
		block,
		parentCSS;

	sel = block.selector + " ";
	dec = block.declarations.join("; \n") + ";";
	parentCSS = sel + beginBlock + dec + endBlock;

	if (!block.children.length) {
		return [parentCSS];
	} else {
		var childrenCSS = block.children.map(blockToCSS).reduce(function(acc, children) {
			return acc.concat(children);
		});
		var prefixedChildrenCSS = childrenCSS.map(function(child) {
			return sel + child;
		});
		prefixedChildrenCSS.unshift([parentCSS]);

		return prefixedChildrenCSS;
	}
};

var output = formatBlocks(lineObjects).map(blockToCSS);