javascript

  var [a=1,b=2,c=4] = [11,34,55];
  console.log(a,b,c);//11 ,34,55

  let [x,,y]=[12,23,45];
  console.log(x,y);//12,45
  let [d,...t]= [12,13,14,15,16];
  console.log(`d:${d}   t:${t}`);//d:12 t:13,14,15,16
  let [u,i,...r] = ["q"];
  console.log(u,i,r);//q undefined  []

解构赋值允许指定默认值。

  let [foo = 'hello']=[];
  console.log(foo);//hello
  let [bar = 'how',too= 'world'] =['teach'];
  console.log(bar,too); //teach world

  let [sh = 2] = [undefined];
  console.log(sh);//2
  let [de = 1] = [null];
  console.log(de);//null