js 深度copy 深复制

 function deepCopy(target,answer) {        var answer = answer ?answer :{};        for (var a in target) {            if(typeof target[a] === "object") {                if(target[a] === null) {                    answer[a] = null;                }                else {                    answer[a] = target[a].constructor ===Array ? [] : {};//后面的：{}其实可以不需要，只是为了好看，有点冗余的味道                    deepCopy(target[a],answer[a]);                }            }            else {                answer[a] = target[a];            }        }        return answer;    }