三中好用的数组去重方式

 var a = [5,6,5,4,‘3‘,{},3,‘字符‘]   

    function unique0() {
        let arr = [];
        for(let i = 0;len = a.length,i < len;i ++){
            if(arr.indexOf(a[i]) === -1){
                arr.push(a[i])
            }
        }
        return arr
    }
    console.log(unique0(a))

    function unique1(a) {
        let ret = [];
        let hash = {};
        for(let i = 0;len = a.length,i < len ;i ++){
            let key = typeof a[i] + a[i]
            if(!hash[key]){
                hash[key] = 1;
                ret.push(a[i])
            }
        }
        return ret
    }
    console.log(unique1(a))

    function unique2(a) {
        let arr = new Set(a)
        return Array.from(arr)
    }
    console.log(unique2(a))