I need to create url for get which is going to accept array, how in node.js/express extract array from request? - node.js

Question

I need to create url for get which is going to accept array, how in node.js/express extract array from request ?
I need to pass array with names which parametes I need to back from Person
model.
/api/person # here I need to pass which fields I want to see but to be generic.

Answer 1

One option is using a JSON format.
http://server/url?array=["foo","bar"]
Server side
var arr = JSON.parse(req.query.array);
Or your own format
http://server/url?array=foo,bar
Server side
var arr = req.query.array.split(',');

Answer 2

Express exposes the query parameter as an array when it is repeated more than once in the request URL:
app.get('/', function(req, res, next) {
console.log(req.query.a)
res.send(200)
}
GET /?a=x&a=y&a=z:
// query.a is ['x', 'y', 'z']
Same applies for req.body in other methods.

Answer 3

You can encode an array in percent encoding just "overwriting" a field, formally concatenating the values.
app.get('/test', function(req,res){
console.log(req.query.array);
res.send(200);
});
localhost:3000/test?array=a&array=b&array=c
This query will print ['a','b','c'].

Answer 4

Using next code:
app.use('/', (req, res) => {
console.log(req.query, typeof req.query.foo, Array.isArray(req.query.foo));
res.send('done');
});
On backend, you have two standard approaches. For next requests:
/?foo=1&foo=2
/?foo[]=1&foo[]=2
your NodeJS backend will receive next query object:
{ foo: [ '1', '2' ] } 'object' true
{ foo: [ '1', '2' ] } 'object' true
So, you can choose the way you want to. My recommendation is the second one, why? If you're expect an array and you just pass a single value, then option one will interpret it as a regular value (string) and no an array.
[I said we have two standards and is not ok, there is no standard for arrays in urls, these are two common ways that exist. Each web server does it in it's own way like Apache, JBoss, Nginx, etc]

Answer 5

If you want to pass an array from url parameters, you need to follow the bellow example:
Url example:
https://website.com/example?myarray[]=136129&myarray[]=137794&myarray[]=137792
To retrieve it from express:
console.log(req.query.myarray)
[ '136129', '137794', '137792' ]

Answer 6

Express has a tool to check if your path will match the route you are creating : Express.js route tester.
As Jose Mato says you have to decide how to structure your url:
?foo=1&foo=2
?foo[]=1&foo[]=2
The http request should look like this, if you chose method 1:
http://baseurl/api/?foo=1&foo=2
Your route should have this logic:
app.get('/api/:person', (req, res) => {
/*This will create an object that you can iterate over.*/
for (let foo of req.params.foo) {
/*Do some logic here*/
}
});

Answer 7

You can pass array elements separated by slashes -
GET /api/person/foo/bar/...
Define your route as '/api/person/(:arr)*'
req.params.arr will have the first parameter.
req.params[0] will have the rest as string.
You split and create an array with these two.
app.get('/api/person/(:arr)*', function(req, res) {
var params = [req.params.arr].concat(req.params[0].split('/').slice(1));
...
});
GET /api/person/foo
params = ["foo"]
GET /api/person/foo/bar
params = ["foo", "bar"]
...

Answer 8

Here use this, '%2C' is the HTML encoding character for a comma.
jsonToQueryString: function (data) {
return Object.keys(data).map((key) => {
if (Array.isArray(data[key])) {
return encodeURIComponent(`${key}=${data[key].map((item) => item).join('%2C')}`);
}
return encodeURIComponent(`${key}=${data[key]}`);
}).join('&');
}
To access the query params
const names = decodeURIComponent(req.query.query_param_name);
const resultSplit = names.split(',');

Answer 9

Theres a problem when the array param contains only one value, because then it behaves like a simple string. Or when it doesn't contain any value.
Eg.:
?arrayParam=5
?
?arrayParam=5&arrayParam=6
Here's a function that always extracts the param with the given name, as an array:
export function extractArrQueryParams(
req: express.Request,
paramName: string
) {
let param = req.query[paramName];
let returnArray = [];
if (Array.isArray(param)) {
for (let e of param) {
returnArray.push(e);
}
} else {
if (param) {
returnArray.push(param);
}
}
return returnArray;
}