老师这里为什么Array(30)会打印两次

function Issues({issues}){
    console.log(issues);
    return (
        <div className="root">
            <div className="issues">
                {
                    issues.map(issue => <IssueItem issue={issue} key={issue.id}/>)
                }
            </div>
            <style jsx>{`
                .issues{
                    border:1px solid #eee;
                    border-radius:5px;
                    margin-bottom:20px;
                    margin-top:20px;
                }
            `}</style>
        </div>
    )
}

这里面打印的