Javascript 条件呈现在我的功能组件中不起作用
如果(age您实际上不需要状态,我将尝试呈现一个组件。只需使用Javascript 条件呈现在我的功能组件中不起作用,javascript,reactjs,react-hooks,jsx,Javascript,Reactjs,React Hooks,Jsx,如果(age您实际上不需要状态,我将尝试呈现一个组件。只需使用const uneligible=age即可{ var dateOfBirth=“2007-01-01”; var split_dob=出生日期分割(“-”); var月=分割月[1]; var日=分割日[2]; var年=分割日[0]; var dob_asdate=新日期(年、月、日); var today=新日期(); var mili_dif=Math.abs(today.getTime()-dob_asdate.getTim
const uneligible=age即可{
var dateOfBirth=“2007-01-01”;
var split_dob=出生日期分割(“-”);
var月=分割月[1];
var日=分割日[2];
var年=分割日[0];
var dob_asdate=新日期(年、月、日);
var today=新日期();
var mili_dif=Math.abs(today.getTime()-dob_asdate.getTime());
风险期限=百万美元/(1000*3600*24*365.25);
控制台日志(年龄);
const uneligible=年龄<18岁;
返回(
{uneligible&&(
获取出生日期
,并将不可触发
设置为标准常量(UseMoom
,以便在需要时进行轻微优化)。这将防止渲染设置状态的循环,设置状态会导致重新渲染,从而设置状态
const{usemo}=React;
常量配置文件页=({dateOfBirth})=>{
const uneligible=useMoom(()=>{
const mili_dif=Math.abs(Date.now()-Date.parse(dateOfBirth));
常数=mili_dif/(1000*3600*24*365.25);
返回年龄<18岁;
},[出生日期];
返回(
{uneligible&&(
这是一个错误警报-请查看!
)}
);
};
ReactDOM.render(
,
根
);
函数会一次又一次地重新呈现,因为您立即设置了状态。
解决方案:
import React from "react";
import Alert from "@material-ui/lab/Alert";
const ProfilePage = (props) => {
const isEligible = () => {
var dateOfBirth = "2007-01-01";
var split_dob = dateOfBirth.split("-");
var month = split_dob[1];
var day = split_dob[2];
var year = split_dob[0];
var dob_asdate = new Date(year, month, day);
var today = new Date();
var mili_dif = Math.abs(today.getTime() - dob_asdate.getTime());
var age = mili_dif / (1000 * 3600 * 24 * 365.25);
console.log(age);
return age < 18;
}
return (
<div>
{isEligible() && (
<Alert variant="filled" severity="error">
This is an error alert — check it out!
</Alert>
)}
</div>
);
};
export default ProfilePage;
从“React”导入React;
从“@material ui/lab/Alert”导入警报;
const ProfilePage=(道具)=>{
常数isEligible=()=>{
var dateOfBirth=“2007-01-01”;
var split_dob=出生日期分割(“-”);
var月=分割月[1];
var日=分割日[2];
var年=分割日[0];
var dob_asdate=新日期(年、月、日);
var today=新日期();
var mili_dif=Math.abs(today.getTime()-dob_asdate.getTime());
风险期限=百万美元/(1000*3600*24*365.25);
控制台日志(年龄);
返回年龄<18岁;
}
返回(
{isEligible()&&(
这是一个错误警报-请查看!
)}
);
};
导出默认配置文件页面;
const [uneligible,setEligible] = React.useState(
false // default value
)
<div>{uneligible&& <Alert variant="filled" severity="error">
This is an error alert — check it out!
</Alert>}</div>
const ProfilePage = (props) => {
var dateOfBirth = "2007-01-01";
var split_dob = dateOfBirth.split("-");
var month = split_dob[1];
var day = split_dob[2];
var year = split_dob[0];
var dob_asdate = new Date(year, month, day);
var today = new Date();
var mili_dif = Math.abs(today.getTime() - dob_asdate.getTime());
var age = mili_dif / (1000 * 3600 * 24 * 365.25);
console.log(age);
const uneligible = age < 18;
return (
<div>
{uneligible && (
<Alert variant="filled" severity="error">
This is an error alert — check it out!
</Alert>
)}
</div>
);
};
import React from "react";
import Alert from "@material-ui/lab/Alert";
const ProfilePage = (props) => {
const isEligible = () => {
var dateOfBirth = "2007-01-01";
var split_dob = dateOfBirth.split("-");
var month = split_dob[1];
var day = split_dob[2];
var year = split_dob[0];
var dob_asdate = new Date(year, month, day);
var today = new Date();
var mili_dif = Math.abs(today.getTime() - dob_asdate.getTime());
var age = mili_dif / (1000 * 3600 * 24 * 365.25);
console.log(age);
return age < 18;
}
return (
<div>
{isEligible() && (
<Alert variant="filled" severity="error">
This is an error alert — check it out!
</Alert>
)}
</div>
);
};
export default ProfilePage;