Using axios for post request and fetching response - reactjs

Question

fetching data from axios response return undefined value when console.logged
I have tried numerous way but the response is always shows undefined
This is the usersdata
const userdatas=[ {id: 1,firstname: "Leanne",lastname:"Gram",password: "123",phone:"9474211442"}**
Client
handleSubmit=(e)=>{
alert(this.state.Firstname)
e.preventDefault();
axios.post('http://localhost:3001/login', {
lastname: JSON.stringify(this.state.Lastname),
firstname: JSON.stringify(this.state.Firstname),
password:JSON.stringify(this.state.password),
phoneno:JSON.stringify(this.state.phoneno)
}).then(res=>alert(res.data.id))
}
]
Express
const userdatas=[ {id: 1,firstname: "Leanne",lastname:"Gram",password: "123",phone:"9474211442"}**
app.post('/login',(req,res)=>{
let logindetail={firstname:req.body.firstname,
password:req.body.password}
logindetail.firstname=logindetail.firstname.replace(/['"]+/g, '')
logindetail.password=logindetail.password.replace(/['"]+/g, '')
var count = Object.keys(userdatas).length;
for(var i=0;i<count;i++)
{
if(logindetail.firstname===userdatas[i].firstname&&logindetail.password===userdatas[i].password)
{
res.json(userdatas[i])
}
}
});

Answer 1

In your Express section, userdatas appears to be an object, but you are trying to look it up like an array in your res.json call. You need to wrap it in Object.keys like you have when you are setting your count value.

Answer 2

Seeing as what you receive on the backend doesn’t appear to be right , I’d revisit the frontend request. IMHO, you ought to only have one JSON.stringify call against the whole object you want to wrap, not a separate call per prop. Try that and then see what the backend receives.

Answer 3

First the userdatas is an object and you are trying to access its values as in an array. Secondly are you sure that the if condition inside the loop gets satisfied once?. Because you can't have multiple responses to a single request. Build a single response body in a variable as you loop. Send it once the loop is finished.
for (var i = 0; i < count; i++) {
if (
logindetail.firstname === userdatas[i].firstname &&
logindetail.password === userdatas[i].password
) {
res.json(userdatas[i]);
}
}
Change it to something like this
let result = [];
for (var i = 0; i < count; i++) {
if (***your corrected condition***) {
result = userdatas[i];
}
}
res.send(result);