对象或数组的深拷贝

function deepCopy(obj,cache){
    if(cache===void 0) cache=[]
    if(obj===null||typeof obj !== "object") return obj
    let hit=cache.filter(i=>i.origin===obj)[0]
    if(hit) return hit.copy
    let copy=Array.isArray(obj)?[]:{}
    cache.push({
        origin:obj,
        copy:copy
    })
    Object.keys(obj).forEach(i=>{
        copy[i]=deepCopy(obj[i],cache)
    })
    return copy
}