1.判断两个数组是否“相等”2.取两个数组的交并差集

var a = [1,2,3,4];
var b = [3,4,5,6];

var set1 = new Set([...a,...b]);
var set2 = new Set(a.filter((item)=>{
    return b.indexOf(item) > -1
}));
var set3 = new Set(a.filter((item)=>{
    return b.indexOf(item) == -1
}))
console.log('并集：',set1);//Set{1,2,3,4,5,6}
console.log('交集：',set2);//Set{3,4}
console.log('差集：',set3);//Set{1,2}

 var a = ['1',2];
 var b = [1,2];
 console.log(JSON.stringify(a));//['1',2]
 console.log(JSON.stringify(b));//[1,2]
 console.log(JSON.stringify(a) == JSON.stringify(b));//false

   Array.prototype.equals = function (arr) {
        if (!arr)
            return false;
        if (this.length != arr.length)
            return false;
        for (var i = 0, l = this.length; i < l; i++) {
            if (Array.isArray(this[i]) && Array.isArray(arr[i])) {
                this[i].equals(arr[i]);
            } 
            //else if(Object.prototype.toString.call(this[i])==='[object Object]' && Object.prototype.toString.call(arr[i])==='[object Object]') {
            //考虑到数组中包含对象，调用判断对象是否"相等"的方法,此方法不考虑数组中有对象的情况
            //}
            else {
                // console.log(this[i]);
                // console.log(arr[i]);
               if(this[i]!=arr[i]){
                   return false;
               }
            }
        }
        return true;
    }

 var a = ['1',2];
 var b = [1,2];
 console.log(a.toString());//1,2
 console.log(b.toString());//1,2
 console.log(a.toString() == b.toString());//true