SOURCE

let rootList = [
  { id: 1, parent: null, text: '菜单1' },
  { id: 11, parent: 1, text: '菜单1-1' },
  { id: 111, parent: 11, text: '菜单1-1-1' },
  { id: 112, parent: 11, text: '菜单1-1-2' },
  { id: 12, parent: 1, text: '菜单1-2' },
  { id: 2, parent: null, text: '菜单2' },
  { id: 21, parent: 2, text: '菜单2-1' },
  { id: 22, parent: 2, text: '菜单2-2' },
];
function getTreeList(rootList,id,list) {
    for(let item of rootList){
        if(item.parent == id){
            list.push(item)
        }
    }
}