How to display information to the user in koajs?

Question

JavaScript

For example, there is this code:

let userRouter = new Router({prefix: '/user'});//koa-router
userRouter.use(authCheck);

userRouter.get('/settings', async (ctx) => {
    await ctx.render('settings',{message: '???'});//Откуда брать сообщение, если это уже другой ctx?
});
userRouter.post('/settings', async (ctx) => {
    const data = ctx.request.body;
    if(!data.email || !data.email.length) ctx.message = 'Введите почту!';
    if(!data.password || !data.password .length) ctx.message = 'Введите пароль!';
    await ctx.redirect('/user/settings');
});

How to display information to the user if he is redirected from this page?
Is it correct to render in two places, for example, if an error occurs, render the same page in a post request, like this:

userRouter.get('/settings', async (ctx) => {
    await ctx.render('settings',{message: false});//#1
});
userRouter.post('/settings', async (ctx) => {
    const data = ctx.request.body;
    let err = false;
    if(!data.email || !data.email.length) err = 'Введите почту!';
    if(!data.password || !data.email.password) err = 'Введите пароль!';
    
    await ctx.render('settings', {message: err});//#2
});

If this is a normal solution, then how to display information, for example, about a successful login, there should clearly be a redirect from the authorization page.

Answer 1

Messages can be saved using koa-session .
For example:

userRouter.post('/settings', async (ctx) => {
    const data = ctx.request.body;
    if(!data.email || !data.email.length) {
        ctx.session.messages.push('Введите почту!');
        ctx.redirect('/user/settings');
    }
});

You can output information like this:

userRouter.get('/settings', async (ctx) => {
    await ctx.render('settings',{message: ctx.session.messages});
});

Also, do not forget about the first visit, when messages do not exist yet:

app.use(async (ctx,next)=>{
    if(!ctx.session.messages) ctx.session.messages = [];
    await next();
});