js 判断循环引用

利用JSON.stringify的报错信息来做

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
var obj2 = {a: {c: "1"}};
obj2.a.b = obj2;
var obj3 = {a: 1, b: 2, c: {d: 4}, d: {}, e: {}}

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
obj1.b.b = obj1.b;

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
obj1.b.b = obj1.b;

var obj4 = {a:"1"};
obj4.b = {c: 1};
obj4.aa = obj4.b;
obj4.bb = obj4.b;

var obj5 = {a:"1"};
obj5.b = {};
obj5.b.a = obj5.b;
obj5.b.b = obj5.b;

var b = {}
var obj6 = {
 a1: b,
 a2: {
     a3: b
  }
}
const isLoop = (originObj) => {
  let rs = ''
  try {
    JSON.stringify(originObj);
  }
  catch(err){
        rs = err // 可执行
  }
  return rs.toString().indexOf('circular') === -1 ? false : true;
}

console.log(isLoop(obj1));
console.log(isLoop(obj2));
console.log(isLoop(obj3));
console.log(isLoop(obj4));
console.log(isLoop(obj5));
console.log(isLoop(obj6));

这里我看了JONS-js的源码，利用weak-map来做

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
var obj2 = {a: {c: "1"}};
obj2.a.b = obj2;
var obj3 = {a: 1, b: 2, c: {d: 4}, d: {}, e: {}}

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
obj1.b.b = obj1.b;

var obj1 = {a:"1"};
obj1.b = {};
obj1.b.a = obj1.b;
obj1.b.b = obj1.b;

var obj4 = {a:"1"};
obj4.b = {c: 1};
obj4.aa = obj4.b;
obj4.bb = obj4.b;

var obj5 = {a:"1"};
obj5.b = {};
obj5.b.a = obj5.b;
obj5.b.b = obj5.b;
const isLoop = (originObj) => {
    let wm = new WeakMap();
    let rs = false;
    function dp(obj) {
        let cwm = new WeakMap();
        if(!wm.has(obj)) {
            wm.set(obj, obj)
        }
        let keys = Object.keys(obj);
        for (let i = 0, len = keys.length; i < len; i++) {
            key = keys[i];
            
            if(typeof obj[key] === 'object') {
                if(cwm.has(obj[key])) {
                    // 如果同层级的互相引用了，终结掉
                    obj[key] = {};
                } else {
                    cwm.set(obj[key], obj[key]);
                }
            }
        }
        for (let i = 0, len = keys.length; i < len; i++) {
            key = keys[i];
            
            if(typeof obj[key] === 'object') {
                if(wm.has(obj[key])) {
                    // 如果循环引用了，终结掉
                    obj[key] = {};
                    rs = true;
                } else {
                    wm.set(obj[key], obj[key])
                }
                dp(obj[key])
            }
        }
    }
    dp(originObj);
    return rs;
}

console.log(isLoop(obj1));
console.log(isLoop(obj2));
console.log(isLoop(obj3));
console.log(isLoop(obj4));
console.log(isLoop(obj5));