Algoritms tasks

Consider a rooted tree. A rooted tree has one special vertex called the root. All edges are directed from the root. Vertex u is called a child of vertex v and vertex v is called a parent of vertex u if there exists a directed edge from v to u. A vertex is called a leaf if it doesn't have children and has a parent.
Let's call a rooted tree a spruce if its every non-leaf vertex has at least 3 leaf children. You are given a rooted tree, check whether it's a spruce.
The definition of a rooted tree can be found here.

            window.onload = function() {
                var indexes,
                    vertexes, 
                    outputAnswer = document.querySelector('.answer span'),
                    inputVertexes = document.querySelector('input[data-function="vertexes"]'),
                    inputIndexes = document.querySelector('input[data-function="indexes"]'),
                    result = 'No';
                    
                    inputVertexes.onchange = function() {
                    readData();
                    isSprute(vertexes, indexes);
                };
            
                inputIndexes.onchange = function() {
                    readData();
                    isSprute(vertexes, indexes);
                };
                
                function readData() {
                    vertexes = +document.querySelector('input[data-function="vertexes"]').value;
                    indexes = document.querySelector('input[data-function="indexes"]').value.split(' ');
                    indexes = changeStringArrToNumber(indexes);
                } 
                
                function changeStringArrToNumber (arr) {
                    for (var i = 0; i < arr.length; i++) {
                        arr[i] = (+arr[i]);
                    }
            
                    return arr;
                }
            
                function isSprute(vertexes, indexes) {        
                    var leafs = [];
            
                    if (checkConditions(vertexes, indexes)) {
                        outputAnswer.innerHTML = result;
                        return;
                    }        
            
                    result = 'No';
            
                    for (var i = 0; i < indexes.length; i++) {
                        if (indexes[i] == 1) {
                            leafs.push(i);
                        } else if (leafs.indexOf(indexes[i]) + 1) {
                            leafs.splice(leafs.indexOf(indexes[i]), 1);
                        }
                    }
                    
                    if (leafs.length >= 3) result = "Yes";
            
                    outputAnswer.innerHTML = result;
                }
            
                function checkConditions(vertexes, indexes) {
                    if (vertexes < 3) {
                        result = 'Incorrect number of vertexes (need start from 3). Please change it.';
                        return true;
                    }
            
                    if (indexes.length != vertexes - 1) {
                        result = 'Incorrect indexes value. Please change it.';
                        return true;
                    }
                
                    for (var i = 0; i < indexes.length; i++) {
                        if (indexes[i] <= 0) {
                            result = 'Value of ' + i + '-th index incorrect. Please change it.';
                            return true;
                        }
                    }
            
                    return false;
                }
            };

Task 4