js如何遍历两个数组，对比判断？

[weixin_45450224]

var a =｛张三，李四，王五｝； var b = ｛张三｝； 我想用b去a里找是否有重复。比如b张三和a张三是一样的。

[usecf]

<script> function find(){ var a =["张三2","李四","王五"]; var b = ["张三"]; if(-1 != a.indexOf(b[0])) { alert("有重复项"); } else { alert("没有找到"); } } window.onload=function(){ find(); } </script>

[usecf]

<script> function find(){ var a =["张三2","李四","王五"]; var b = ["张三"]; var flag =false; for(var i=0; i<a.length;i++) { if(a[i] == b[0]) { flag = true; break; } else { flag = false; continue; } } if(flag) { alert("有重复项"); } else { alert("没有找到"); } } window.onload=function(){ find(); } </script>

[孤独与酒伴我同行]

双重for循环，简单粗暴！！！

[ZionHH]

let a = ['张三', '李四', '王五']
let b = ['李四']
let flag = a.findIndex(aItem => b.some(bItem => bItem === aItem))

[天际的海浪]

var a = ['张三', '李四', '王五'];
var b = ['李四'];
var x = b.some(function(v, i){
	return a.indexOf(v)!=-1;
});
alert(x?"有重复":"没有重复");

[乐予忘忧]

let a = ['张三','李四','王五']
let b = ['张三','张三']
function duplication(arr1,arr2){
    let newArr1 = Array.from(new Set(arr1))
    let newArr2 = Array.from(new Set(arr2))
    let less = newArr1
    let more = newArr2
    //数组去重,同时做标记
    if(arr1.length > arr2.length){
        more = newArr1
        less = newArr2
    }
    //检查去重后的长度设置长度短的为less, 长的为more
    let repeated = less.filter(item=> more.includes(item))
    //遍历短的数组进行返回到重复的数组
    console.log(`重复字段如下${repeated.join()}`)
    //输出结果提示
}
duplication(a,b)