JavaScript 如何从地图数组中获取长度

Question

我是 JSX 的新手，我正在尝试获取每个团队的员工人数this.state.teams[0].employee.length会给我数组中[0]对象的员工人数，我怎么能获取每个团队的员工人数并且只渲染一次？

render() {
    const {teams, isLoading} = this.state;
    const { location } = this.props;

    if (isLoading) {
        return <p>Loading...</p>;
    }
    // console.log("Number of Employees team", this.state.teams[0].employee.length);
    

    const teamList = teams.map(team => {

        console.log("TEAM Employees", teams[0].employee.length);

        return <tr key={team.id}>
               <td>
                <div className="tableContent">
                    <div>
                         {team.name} 
                    </div>
                    <div>
                      <ul>{team.employee.map(employee => {
                       return <li key={employee.id}>{employee.name}: {employee.email}</li>
                      })}</ul>
                    </div>
                    <div>
                     {team.employee.map(employee => {
                       return <li key={employee.id}>{teams[0].employee.length}</li>
                      })}
                    </div>
                </div>                    
            </td>
        </tr>
    });

Answer 1

您可以针对特定团队尝试此操作：

const teamList = teams.map(team => {
   console.log("TEAM Employees", team.employee.length);
}

或者这对于所有团队的员工人数：

const numberOfAllEmployees = teams.map(team => team.employee.length).reduce((a,b) => a + b);

Answer 2

您可以使用Object.keys(teams[0].employee).length

Object.keys() 方法返回给定对象自己的可枚举属性名称的数组，以与普通循环相同的顺序迭代。 MDN