I have a JavaScript loop iterating over an array. For every item, I perform a fetch request to insert the object. If the server response indicates it is an already inserted object, I try an update operation with another fetch call.
As the requests are asynchronous, the loop sets the request object to the next insert item before I try the update operation, so I end up requesting an update for an object it's not yet inserted.
Is there any way I can access the request object used for this fetch operation, so I can use that object instead of the loop var?
I've tried with this
within the promise method, but it returns a reference to the window object: console.log(this) ==> > Window http://localhost
My code:
for (var i = 0; i < expectedRows; i++) {
var row = myArray[i];
customerCode = row['customer_code'];
customerName = row['customer_name'];
customerBalance = row['customer_balance'];
// Build body call
var callBody = {
user: 'USER',
code: customerCode,
name: customerName,
balance: customerBalance
};
var fetchOptions = {
method: "POST",
cache: "no-cache",
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
redirect: "error",
referrer: "ux-import",
body: JSON.stringify(callBody),
};
// Call
var epurl = baseEP + '/customer/create';
fetch(epurl, fetchOptions)
.then(response => response.json())
.then(response => {
console.log(this) // <== Window object reference
if (response.error === 0) {
console.log('insert ok');
insertRows++;
} else {
if (response.error == 2) {
console.log('insert error => update');
var updateEP = baseEP + '/customer/update';
fetch(updateEP, fetchOptions) // <== Not what you expect
.then(updResponse => updResponse.json())
.then(updResponse => {
if (updResponse.error === 0) {
console.log('update ok.')
updateRows++;
} else {
console.log('update error: ' + updResponse.msg)
errorMessages.push(updResponse.msg);
}
})
.catch(error => {
console.log('update failure');
errorMessages.push(error);
});
} else {
console.log('insert error.');
errorMessages.push(response.msg);
}
}
})
.catch(error => {
console.log('insert failure.');
errorMessages.push(error);
});
}
I need some way to access this fetch call request object to achieve something like this:
var updFetchOptions = {
method: "POST",
cache: "no-cache",
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
redirect: "error",
referrer: "ux-import",
body: this.request.body, // this as a reference to this fetch's request
}
fetch(updateEP, updFetchOptions)...
:
:
Can you try this.
for (let i = 0; i < expectedRows; i++) {
let row = myArray[i];
customerCode = row['customer_code'];
customerName = row['customer_name'];
customerBalance = row['customer_balance'];
// Build body call
let callBody = {
user: 'USER',
code: customerCode,
name: customerName,
balance: customerBalance
};
let fetchOptions = {
method: "POST",
cache: "no-cache",
headers: {
"Content-Type": "application/x-www-form-urlencoded",
},
redirect: "error",
referrer: "ux-import",
body: JSON.stringify(callBody),
};
// Call
let epurl = baseEP + '/customer/create';
fetch(epurl, fetchOptions)
.then(response => response.json())
.then(response => {
console.log(this) // <== Window object reference
if (response.error === 0) {
console.log('insert ok');
insertRows++;
} else {
if (response.error == 2) {
console.log('insert error => update');
let updateEP = baseEP + '/customer/update';
fetch(updateEP, fetchOptions) // <== Not what you expect
.then(updResponse => updResponse.json())
.then(updResponse => {
if (updResponse.error === 0) {
console.log('update ok.')
updateRows++;
} else {
console.log('update error: ' + updResponse.msg)
errorMessages.push(updResponse.msg);
}
})
.catch(error => {
console.log('update failure');
errorMessages.push(error);
});
} else {
console.log('insert error.');
errorMessages.push(response.msg);
}
}
})
.catch(error => {
console.log('insert failure.');
errorMessages.push(error);
});
}
Basically, defining variables with var
is not a good method as it doesn't maintain its state with each iteration of loop. But using let
maintains the variable state for each iteration and you can use the variable even after doing some async task like fetch
in your case.