getTreeLeaves.js

export const getTreeLeaves = (tree: any, getChildren = (node: any) => node && node.children) => {
    const leaves = [];
    const nodes = Array.isArray(tree) ? [...tree] : [tree];
    let node;
    let children;
    while (
        // tslint:disable-next-line:no-conditional-assignment ban-comma-operator
        node = nodes.shift(), children = getChildren(node),
        ((children && children.length) || (leaves.push(node) && nodes.length))
    ) {
        if (children) {
            nodes.push(...children);
        }
    }
    return leaves;
};