var findLargestLevel = function(node) {
    var levelSum = {};
    levelSum[0] = node.value;
    var levels = [1];

    var sumNodes = function(node, level) {
        for (var i = 0; i < node.children.length; i ++) {
            if (!levelSum[level]) {
                levelSum[level] = node.children[i].value;
            } else {
                levelSum[level] += node.children[i].value;
            }
            sumNodes(node.children[i], levels.push(levels[i])[levels.length-1]);
        }
    }
    sumNodes(node, levels[0]);

    var largestLevel = 0;
    for (var key in levelSum) {
        if (key === 'undefined') {
            levelSum[Object.keys(levelSum).length - 1] = levelSum[key];
        }
        if (levelSum[key] > largestLevel) {
            largestLevel = key;
        }
    }
    return largestLevel;
};

var t = {value: 2, children: [
    {value: 3, children: [
        {value: 2, children: []},
        {value: -7, children: []},
    ]},
    {value: -1, children: [
        {value: 5, children:[]},
        {value: 4, children: []}
    ]}
]};

console.log(t);
var x = findLargestLevel(t);
console.log(x)