reduce

tree.js

const tree = {
		name: '/',
		children:
			[
				{
					name: 'eTc', children: [
						{
							name: 'config.json',
							meta: {},
							type: 'file'
						}
					],
					meta: {},
					type: 'directory'
				},
				{
					name: 'hOsts',
					meta: {},
					type: 'file'
				}
			],
		meta: {},
		type: 'directory'
	}

	function check(obj, type, num) {
		return obj.type === type ? num + 1 : num;
	}

	let reduce = (obj, type, num) => {
		let {children} = obj;
		let newNum = check(obj, type, num);

		if(!children) {
			return newNum;
		}
		return children.reduce((acc, cur) => {
			return reduce(cur, type, acc)
		}, newNum)
	};
	
	console.log(reduce(tree, 'directory', 0));