beat-permutations/drums.js

const numBeats = Math.ceil(Math.random()*9);

let resultString = '';
const appendages = [ 'lh', 'rh', 'lf', 'rf' ];

for(let appendage of appendages){
	let resultString = '';
	for(let i = 1; i <= numBeats; i++){
		const hit = Math.floor(Math.random()*2);
		if(hit === 1){
			resultString += appendage + ' ';
		} else {
			resultString += '   ';
		}

	}
	console.log(resultString);
}

const breakDown = (node)=>{

	if(node.value < 4){
		return node
	}

	//2 path
	node.twoPath = {};
	node.twoPath.left = { value: 2 }
	node.twoPath.right = breakDown({value:node.value-2})

	//3 path
	if(node.value > 4){
		node.threePath = {}
		node.threePath.left = { value: 3 }
		node.threePath.right = breakDown({value:node.value-3})
	}

	return node;
}

const tree = breakDown({value:numBeats});

//console.dir(tree, {depth:null});

const getLeaves = (node)=>{
	if(node.twoPath === undefined){
		return node.value;
	}

	let twoPathResult = [];
	const twoPathLeftValue = getLeaves(node.twoPath.left);
	const twoPathRightValue = getLeaves(node.twoPath.right);
	if(Number.isInteger(twoPathRightValue)){
		twoPathResult[0] = twoPathLeftValue;
		twoPathResult[1] = twoPathRightValue;
	} else {
		if(Number.isInteger(twoPathRightValue[0])){
			twoPathRightValue.unshift(twoPathLeftValue);
		} else {
			for(let subArray of twoPathRightValue){
				subArray.unshift(twoPathLeftValue);
			}
		}
		twoPathResult = twoPathRightValue;
	}

	let threePathResult = [];
	if(node.threePath !== undefined){
		const threePathLeftValue = getLeaves(node.threePath.left);
		const threePathRightValue = getLeaves(node.threePath.right);
		if(Number.isInteger(threePathRightValue)){
			threePathResult[0] = threePathLeftValue;
			threePathResult[1] = threePathRightValue;
		} else {
			if(Number.isInteger(threePathRightValue[0])){
				threePathRightValue.unshift(threePathLeftValue);
			} else {
				for(let subArray of threePathRightValue){
					subArray.unshift(threePathLeftValue);
				}
			}
			threePathResult = threePathRightValue;
		}
	}
	
	if(threePathResult.length === 0){
		return twoPathResult;
	} else {
		if(Number.isInteger(twoPathResult[0])){
			if(Number.isInteger(threePathResult[0])){
				return [twoPathResult, threePathResult]
			} else {
				const result = [twoPathResult];
				result.push(threePathResult[0]);
				return result;
			}
		} else {
			if(Number.isInteger(threePathResult)){
				twoPathResult.push(threePathResult)
			} else {
				if(Number.isInteger(threePathResult[0])){
					twoPathResult.push(threePathResult)
				} else {
					twoPathResult = twoPathResult.concat(threePathResult);
				}
			}
			return twoPathResult;
		}
	}
}
const claves = getLeaves(tree);
if(Number.isInteger(claves)){
	console.log(claves);
} else {
	if(Number.isInteger(claves[0])){
		console.log(claves);
	} else {
		const clave = claves[Math.floor(Math.random()*claves.length)];
		console.log(clave);
	}
}