二进制搜索树上的Javascript大小

Question

I have done this is c++ because you can pass in a parameter by reference. I am having trouble figuring out how to do this in JavaScript. What do I need to change in my code? My output is 1

this.sizeOfBst = function(){
    size = 0;

    return sizeHelper(this.root, size);
}

function sizeHelper(node, size){
    if(node){
        sizeHelper(node.left, size);
        size++;
        sizeHelper(node.right, size);
    }
    return size
}

Answer 1

Numbers cannot be passed by reference in Javascript. Instead, have sizeHelper return the size and add that size to the total.

function sizeHelper(node) {
    if (node) {
        return 1 + sizeHelper(node.left) + sizeHelper(node.right);
    }
    return 0;
}

Then it can be used like

this.sizeOfBst = function() {
    return sizeHelper(this.root);
}