SOURCE

const res = [
    {
        name:'a',
        children:[
            {
                name:'b',
                children:[]
            }
        ]
    },
    {
        name:'c',
        children:[
            {
                name:'d',
                children:[
                    {
                    name:'e',
                    children:[]
                  }
                ]
            }
        ]
    },
]

let arr = []
function loop(children){
    if(children.length){
        children.forEach(d=>{
            arr.push(d.name);
            loop(d.children)
        })
    }
}
loop(res);
console.log(arr);