Javascript: nested fetch with foreach loop..? - javascript

this is my problem: I need to make some fetch POST requests to my server. The server holds a list of names. Each name corresponds to a list of elements which I need to browse, in order to find a specific element from all the lists.
I have to work with this structure, can't change it.
My approach was to write a fetch request, to get the all these names (of the lists I need to browse), then I would loop through each name and fetch to get the according lists from the server. Once I get these lists I can loop through the elements till I find the correct element.
This is not an easy task for me as I am new to javascript.
This is how I implemented this:
function browse(){
fetch(TARGET_IP, {
method: "POST",
headers: {
"Content-type": "application/json",
"X-Auth-Token": AUTH_TOKEN
},
body: JSON.stringify({
"id": messageId++,
"jsonrpc": "2.0",
"method": "Browse",
"params": {
"mode": "children"
}
})
})
.then(response => response.json())
.then((data) => {
data.results = Object.assign(Array.prototype, data.result);
data.results.forEach(element => {
if (element.datatype == "datablock") {
datablocks.push(element.name)
}
})
return datablocks;
})
.then((datablocks) => {
datablocks.forEach(element => {
browseDatablocks(element)
})
})
.catch(e => console.error(e))
}
function browseDatablocks(dbname) {
fetch(TARGET_IP, {
method: "POST",
headers: {
"Content-type": "application/json",
"X-Auth-Token": AUTH_TOKEN
},
body: JSON.stringify({
"id": messageId++,
"jsonrpc": "2.0",
"method": "Browse",
"params": {
"var": "\"" + dbname + "\"",
"mode": "children"
}
})
})
.then(response => response.json())
.then((data) => {
data.results = Object.assign(Array.prototype, data.result);
data.results.forEach(element => {
if (element.name == "P_Index")
{
console.warn(dbname);
// This is the element I need and would save it
}
})
})
.catch(e => console.error(e))
}
Now all sorts of strange things happen with this approach.
The console outputs elements that are just not the elements I search for, which is just wrong as I checked on server side.
Some requests are not even handled.
I assume these problems occur because I send too many requests at the same time (the nested ones in browseDatablocks).
How can I handle one request and then the next one? Or are there other ways to implement this?
Thanks.


looks like what you need is Promise.all.
if i understand the problem correctly:
first return the fetch result in function browseDatablocks(dbname)
...
function browseDatablocks(dbname) {
return fetch(TARGET_IP, {
....
And return the value, in last then
.then((data) => {
data.results = Object.assign(Array.prototype, data.result);
const filtered = data.results.filter((element) => element.name == "P_Index");
return filtered;
});
Then in function browse(), last then:
.then((datablocks) => {
const results = datablocks.map(element => browseDatablocks(element));
return Promise.all(results);
})
.then((listOfResults) => {
// Some magic here
})
// Edit or to do them in order:
In function browseDatablocks(dbname), last then:
do the handling, and return a bool instead of filtered eg true = all done, false fetch the next. Something like:
.then((data) => {
data.results = Object.assign(Array.prototype, data.result);
const found = data.results.find(element => element.name == "P_Index");
if (found) {
// Some handling
return true;
}
return false;
})
And in function browse(), last then
.then(async (datablocks) => {
let i = 0;
while(i < datablocks.length) {
const handled = await browseDatablocks(datablocks[i]);
if (handled === true) {
break;
}
i += 1;
}
});

Related

How to run a Node script

I need to be able to run a node script to delete an object from an external API. So I should be able to run this command:
node server.js Customer55555
And it should delete the object.
I have called to the API by using Axios.
const axios = require("axios");
const API = "http://dummy.restapiexample.com/api/v1/employees";
function getAllEmployees() {
axios
.get("http://dummy.restapiexample.com/api/v1/employees")
.then(response => {
// console.log(response.data);
console.log(response.status);
function filterEmployee() {
const employeeData = response.data;
employeeData.filter(employee => {
console.log(employee);
});
// console.log(employeeData);
}
filterEmployee();
})
.catch(error => {
console.log(error);
});
}
function deleteEmployee() {
axios({
method: "DELETE",
url: "http://dummy.restapiexample.com/api/v1/delete/36720",
headers: { "Content-Type": "application/json" }
})
.then(
// Observe the data keyword this time. Very important
// payload is the request body
// Do something
console.log("user deleted")
)
.catch(function(error) {
// handle error
console.log(error);
});
}
// getAllEmployees();
deleteEmployee();
I am able to get an individual object, but I need to figure out how to delete it by running the command above.

You can do something like this:
const axios = require("axios")
const API = "http://dummy.restapiexample.com/api/v1/employees"
async function getAllEmployees(filter = null) {
try {
const response = await axios.get("http://dummy.restapiexample.com/api/v1/employees")
console.log(response.status)
let employeeData = response.data
if (filter) {
// return only employees whose name contains filter.name
employeeData = employeeData.filter(({ employee_name }) => {
return employee_name.toLowerCase().indexOf(filter.name.toLowerCase()) >= 0
})
}
return employeeData
} catch(error) {
console.error(error)
return []
}
}
async function deleteEmployee({ id }) {
if (!id) {
throw new Error('You should pass a parameter')
}
try {
const response = await axios({
method: "DELETE",
url: `http://dummy.restapiexample.com/api/v1/delete/${id}`,
headers: { "Content-Type": "application/json" }
})
console.log("user deleted " + id)
} catch(error) {
// handle error
console.error(error)
}
}
async function main(params) {
const employees = await getAllEmployees({ name: params[0] || '' })
// Returns a promise to wait all delete promises
return Promise.all(employess.map(employee => deleteEmployee(employee)))
}
// process.argv contains console parameters. (https://stackoverflow.com/questions/4351521/how-do-i-pass-command-line-arguments-to-a-node-js-program)
main(process.argv.slice(2)).then(() => {
// returns 0 (Success) (https://stackoverflow.com/questions/5266152/how-to-exit-in-node-js)
process.exit(0)
}).catch(() => {
// returns 1 (error)
process.exit(1)
})
You should adapt this sample to get proper filtering and error reporting.

How to access the request object in a fetch then/response function

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.

You can achieve this by explicitly creating the RequestInit-Object and wrapping your handler functions like this:
const initObject = {
method: 'POST',
something: 1234
};
fetch('/test.json', initObject)
.then(r => r.json())
.then(((initObject) => {
return json => {
console.log({json, initObject})
}
})(initObject));

React - how to get async data from fetch POST

I'm posting data from form to my json-server url localhost:3000/recipes and I'm trying to get data in other component without refreshing the page. I'm posting some data to recipes url and when i go back to other hashURL on page I need to refresh my page to get result. Is there any way to get data async from life cycles or something similar ?
componentDidMount() {
recipesService.then(data => {
this.setState({
recipes: data
});
});
}
recipe.service
const url = "http://localhost:3000/recipes";
let recipesService = fetch(url).then(resp => resp.json());
let sendRecipe = obj => {
fetch(url, {
method: "POST",
headers: {
Accept: "application/json",
"Content-Type": "application/json"
},
body: JSON.stringify(obj)
})
.then(resp => resp.json())
.then(data => console.log(data))
.catch(err => console.log(err));
};
module.exports = {
recipesService,
sendRecipe
};

Probably you want to use something like Redux. :)
Or you can create your cache for this component:
// cache.js
let value;
export default {
set(v) { value = v; },
restore() { return value; },
};
// Component.js
import cache from './cache';
...
async componentDidMount() {
let recipes = cache.restore();
if (!recipes) {
recipes = await recipesService;
cache.set(recipes);
}
this.setState({ recipes });
}

POST request based on array of GET requests

I have array of customers and addresses endpoint URL as below
customerArray = [
{name:customer1, id: 1, address: {streetName: '123 lane'}},
{name:customer2, id: 2, address: {streetName: 'xyz lane'}},
{name:customer3, id: 3, address: {streetName: 'abc lane'}}
]
URL = 'id/addresses'
GET request for URL will return array of addresses based on customer ID
if we get empty array as response then we need to add address from "customerArray" for that id
// This is what I am doing to meet the requirement - seems this is not the right approach. Please help me to fix this
customerArray.forEach((customer) => {
const getObj = {
url: `${customer.id}/addresses`,
method: GET
};
axios(getObj)
.then((getResult) => {
if (getResult.length === 0) {
const postObj = {
url: `${customer.id}/addresses`,
method: POST,
data: customer.address
};
axios(postObj)
.then((postResult) => {
// I am not sure what to do here - I leaving blank so iteration will continue
})
.catch((err) => {
res.status(400).json(err);
});
}
})
.catch((err) => {
res.status(400).json(err);
});
});
Please help me to fix it

I think you don't know how to get the final data. Basically, you should put your promises into an array and you Promise.all to wait for all of them to finish.
Please comment if something wrong. Hope this helps
const promises = customerArray.map((customer) => {
const getObj = {
url: `${customer.id}/addresses`,
method: GET
};
return axios(getObj)
.then((getResult) => {
if (getResult.length === 0) {
return {
url: `${customer.id}/addresses`,
method: POST,
data: customer.address
};
}
return null;
})
.then((postObj) => {
if (postObj) {
return axios(postObj)
}
return null
})
});
Promise.all(promises)
.then(result => {
// the result is a list of data from axios(postObj)
console.log(result);
res.json(result);
})
.catch((err) => {
res.status(400).json(err);
});

Javascript: Fetch DELETE and PUT requests

I have gotten outside of GET and POST methods with Fetch. But I couldn't find any good DELETE and PUT example.
So, I ask you for it. Could you give a good example of DELETE and PUT methods with fetch. And explain it a little bit.

Here is a fetch POST example. You can do the same for DELETE.
function createNewProfile(profile) {
const formData = new FormData();
formData.append('first_name', profile.firstName);
formData.append('last_name', profile.lastName);
formData.append('email', profile.email);
return fetch('http://example.com/api/v1/registration', {
method: 'POST',
body: formData
}).then(response => response.json())
}
createNewProfile(profile)
.then((json) => {
// handle success
})
.catch(error => error);

Ok, here is a fetch DELETE example too:
fetch('https://example.com/delete-item/' + id, {
method: 'DELETE',
})
.then(res => res.text()) // or res.json()
.then(res => console.log(res))

For put method we have:
const putMethod = {
method: 'PUT', // Method itself
headers: {
'Content-type': 'application/json; charset=UTF-8' // Indicates the content
},
body: JSON.stringify(someData) // We send data in JSON format
}
// make the HTTP put request using fetch api
fetch(url, putMethod)
.then(response => response.json())
.then(data => console.log(data)) // Manipulate the data retrieved back, if we want to do something with it
.catch(err => console.log(err)) // Do something with the error
Example for someData, we can have some input fields or whatever you need:
const someData = {
title: document.querySelector(TitleInput).value,
body: document.querySelector(BodyInput).value
}
And in our data base will have this in json format:
{
"posts": [
"id": 1,
"title": "Some Title", // what we typed in the title input field
"body": "Some Body", // what we typed in the body input field
]
}
For delete method we have:
const deleteMethod = {
method: 'DELETE', // Method itself
headers: {
'Content-type': 'application/json; charset=UTF-8' // Indicates the content
},
// No need to have body, because we don't send nothing to the server.
}
// Make the HTTP Delete call using fetch api
fetch(url, deleteMethod)
.then(response => response.json())
.then(data => console.log(data)) // Manipulate the data retrieved back, if we want to do something with it
.catch(err => console.log(err)) // Do something with the error
In the url we need to type the id of the of deletion: https://www.someapi/id

Just Simple Answer.
FETCH DELETE
function deleteData(item, url) {
return fetch(url + '/' + item, {
method: 'delete'
})
.then(response => response.json());
}

Here is good example of the CRUD operation using fetch API:
“A practical ES6 guide on how to perform HTTP requests using the Fetch API” by Dler Ari https://link.medium.com/4ZvwCordCW
Here is the sample code I tried for PATCH or PUT
function update(id, data){
fetch(apiUrl + "/" + id, {
method: 'PATCH',
body: JSON.stringify({
data
})
}).then((response) => {
response.json().then((response) => {
console.log(response);
})
}).catch(err => {
console.error(err)
})
For DELETE:
function remove(id){
fetch(apiUrl + "/" + id, {
method: 'DELETE'
}).then(() => {
console.log('removed');
}).catch(err => {
console.error(err)
});
For more info visit Using Fetch - Web APIs | MDN https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch > Fetch_API.

Some examples:
async function loadItems() {
try {
let response = await fetch(`https://url/${AppID}`);
let result = await response.json();
return result;
} catch (err) {
}
}
async function addItem(item) {
try {
let response = await fetch("https://url", {
method: "POST",
body: JSON.stringify({
AppId: appId,
Key: item,
Value: item,
someBoolean: false,
}),
headers: {
"Content-Type": "application/json",
},
});
let result = await response.json();
return result;
} catch (err) {
}
}
async function removeItem(id) {
try {
let response = await fetch(`https://url/${id}`, {
method: "DELETE",
});
} catch (err) {
}
}
async function updateItem(item) {
try {
let response = await fetch(`https://url/${item.id}`, {
method: "PUT",
body: JSON.stringify(todo),
headers: {
"Content-Type": "application/json",
},
});
} catch (err) {
}
}

Let me simplify this, you can straight up copy the code.
This is for PUT method :
fetch('https://reqres.in/api/users', + id {
method: 'PUT',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify({
name: 'user'
})
})
.then(res => {
return res.json()
})
.then(data => console.log(data))
and this is for DELETE :
fetch('https://reqres.in/api/users' + id, {
method: 'DELETE',
})
.then(res => {
return res.json()
})
.then(data => console.log(data))
Note: I'm using dummy api here.

This is what worked for me when using the PUT method. This method allows me to effectively update the 1st item using my first name:
fetch('https://reqres.in/api/users', {
method: 'PUT',
headers: {
'Content-Type': 'application/json'
},
body: JSON.stringify({
id: 1,
first_name: 'Anthony'
})
})
.then(res => {
return res.json()
})
.then(data => console.log(data))

Here are examples for Delete and Put for React & redux & ReduxThunk with Firebase:
Update (PUT):
export const updateProduct = (id, title, description, imageUrl) => {
await fetch(`https://FirebaseProjectName.firebaseio.com/products/${id}.json`, {
method: "PATCH",
header: {
"Content-Type": "application/json",
},
body: JSON.stringify({
title,
description,
imageUrl,
}),
});
dispatch({
type: "UPDATE_PRODUCT",
pid: id,
productData: {
title,
description,
imageUrl,
},
});
};
};
Delete:
export const deleteProduct = (ProductId) => {
return async (dispatch) => {
await fetch(
`https://FirebaseProjectName.firebaseio.com/products/${ProductId}.json`,
{
method: "DELETE",
}
);
dispatch({
type: "DELETE_PRODUCT",
pid: ProductId,
});
};
};

const DeleteBtn = (id) => {
fetch(`http://localhost:8000/blogs/${id}`, {
method: "DELETE"
})
.then(() => {
navigate('/');
});
}
<button onClick={(event) => { DeleteBtn(blog.id)} }>delete</button>

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