Is there a standard way of passing an array through a query string?
To be clear, I have a query string with multiple values, one of which would be an array value. I want that query string value to be t开发者_JAVA技巧reated as an array- I don't want the array to be exploded so that it is indistinguishable from the other query string variables.
Also, according to this post answer, the author suggests that query string support for arrays is not defined. Is this accurate?
EDIT:
Based on @Alex's answer, there is no standard way of doing this, so my follow-up is then what is an easy way to recognize that the parameter I'm reading is an array in both PHP and Javascript?
Would it be acceptable to name multiple params the same name, and that way I would know that they belong to an array? Example:
?myarray=value1&myarray=value2&myarray=value3...
Or would this be a bad practice?
Here's what I figured out:
Submitting multi-value form fields, i.e. submitting arrays through GET/POST vars, can be done several different ways, as a standard is not necessarily spelled out.
Three possible ways to send multi-value fields or arrays would be:
?cars[]=Saab&cars[]=Audi(Best way- PHP reads this into an array)?cars=Saab&cars=Audi(Bad way- PHP will only register last value)?cars=Saab,Audi(Haven't tried this)
Form Examples
On a form, multi-valued fields could take the form of a select box set to multiple:
<form>
<select multiple="multiple" name="cars[]">
<option>Volvo</option>
<option>Saab</option>
<option>Mercedes</option>
</select>
</form>
(NOTE: In this case, it would be important to name the select control some_name[], so that the resulting request vars would be registered as an array by PHP)
... or as multiple hidden fields with the same name:
<input type="hidden" name="cars[]" value="Volvo">
<input type="hidden" name="cars[]" value="Saab">
<input type="hidden" name="cars[]" value="Mercedes">
NOTE: Using field[] for multiple values is really poorly documented. I don't see any mention of it in the section on multi-valued keys in Query string - Wikipedia, or in the W3C docs dealing with multi-select inputs.
UPDATE
As commenters have pointed out, this is very much framework-specific. Some examples:
Query string:
?list_a=1&list_a=2&list_a=3&list_b[]=1&list_b[]=2&list_b[]=3&list_c=1,2,3
Rails:
"list_a": "3",
"list_b":[
"1",
"2",
"3"
],
"list_c": "1,2,3"
Angular:
"list_a": [
"1",
"2",
"3"
],
"list_b[]": [
"1",
"2",
"3"
],
"list_c": "1,2,3"
(Angular discussion)
See comments for examples in node.js, Wordpress, ASP.net
Maintaining order: One more thing to consider is that if you need to maintain the order of your items (i.e. array as an ordered list), you really only have one option, which is passing a delimited list of values, and explicitly converting it to an array yourself.
A query string carries textual data so there is no option but to explode the array, encode it correctly and pass it in a representational format of your choice:
p1=value1&pN=valueN...
data=[value1,...,valueN]
data={p1:value1,...,pN:valueN}
and then decode it in your server side code.
I don't think there's a standard.
Each web environment provides its own 'standard' for such things. Besides, the url is usually too short for anything (256 bytes limit on some browsers). Of course longer arrays/data can be send with POST requests.
However, there are some methods:
There's a PHP way, which uses square brackets (
[,]) in URL queries. For example a query such as?array_name[]=item&array_name[]=item_2has been said to work, despite being poorly documented, with PHP automatically converting it into an array. Source: https://stackoverflow.com/a/9547490/3787376Object data-interchange formats (e.g. JSON - official website, PHP documentation) can also be used if they have methods of converting variables to and from strings as JSON does.
Also an url-encoder (available for most programming languages) is required for HTTP get requests to encode the string data correctly.
Although the "square brackets method" is simple and works, it is limited to PHP and arrays.
If other types of variable such as classes or passing variables within query strings in a language other than PHP is required, the JSON method is recommended.
Example in PHP of JSON method (method 2):
$myarray = array(2, 46, 34, "dfg");
$serialized = json_encode($myarray)
$data = 'myarray=' . rawurlencode($serialized);
// Send to page via cURL, header() or other service.
Code for receiving page (PHP):
$myarray = json_decode($_GET["myarray"]); // Or $_POST["myarray"] if a post request.
This works for me:
In link, to attribute has value:
to="/filter/arr?fruits=apple&fruits=banana"
Route can handle this:
path="/filter/:arr"
For Multiple arrays:
to="filter/arr?fruits=apple&fruits=banana&vegetables=potato&vegetables=onion"
Route stays same.
SCREENSHOT
UPDATE: In order to achieve this string structure, query-string is the best package.
For example:
import { stringify, parse } from 'query-string';
const queryParams={
fruits:['apple','banana'],
vegetables:['potato','onion']
}
//arrayFormat can be bracket or comma
stringify(queryParams, { arrayFormat: 'bracket' });
Although there isn't a standard on the URL part, there is more or less a standard for JavaScript.
The Array.toString method returns a comma-separated string of items.
Due to this, if you pass objects containing arrays to URLSearchParams, and call toString() on it, it will in turn call toString on each value, resulting in something like this:
let data = {
name: 'abc',
values: ['abc', 123]
}
new URLSearchParams(data).toString();
// ?name=abc&values=abc,123 (with escaped comma characters)
This format is really easy to serialize on the frontend and to parse on any server, besides being easy to understand regardless of context, so it tends to be my go-to for sending array data in URLs.
Note that the query-string module lists the different types of array encoding it supports (https://www.npmjs.com/package/query-string):
For instance {foo: ['1', '2', '3']} can be encoded as:
'foo[]=1&foo[]=2&foo[]=3'
'foo[0]=1&foo[1]=2&foo[3]=3'
'foo=1,2,3'
'foo=1&foo=2&foo=3'
// Any custom separator can be used:
'foo=1|2|3'
// ... and more custom formats
This shows that there are many solutions adopted out there...
I feel it would be helpful for someone who is looking for passing the array in a query string to a servlet. I tested below query string and was able to get the array values using req.getgetParameterValues(); method. Below is the query string I passed through browser.
http://localhost:8080/ServletsTutorials/*.html?
myname=abc&initial=xyz&checkbox=a&checkbox=b
checkbox is my parameter array here.
I use React and Rails. I did:
js
let params = {
filter_array: ['A', 'B', 'C']
}
...
//transform params in URI
Object.keys(params).map(key => {
if (Array.isArray(params[key])) {
return params[key].map((value) => `${key}[]=${value}`).join('&')
}
}
//filter_array[]=A&filter_array[]=B&filter_array[]=C
You mention PHP and Javascript in your question, but not in the tags. I reached this question with the intention of passing an array to an MVC.Net action.
I found the answer to my question here: the expected format is the one you proposed in your question, with multiple parameters having the same name.
You can use http_build_query to generate a URL-encoded querystring from an array in PHP. Whilst the resulting querystring will be expanded, you can decide on a unique separator you want as a parameter to the http_build_query method, so when it comes to decoding, you can check what separator was used. If it was the unique one you chose, then that would be the array querystring otherwise it would be the normal querystrings.
You can use those functions, but make sur you don't use '-' on your object keys.
// convert obj to url params
function objToUrlParams(obj) {
let toUrlParams = (obj, prefex = '') => {
// create url params
let urlParams = "";
// loop through obj
for (let key in obj) {
let val = obj[key];
if (val == null) continue;
if (val == undefined) continue;
// if(val == '') continue;
// if val is an object then call toUrlParams
if (val instanceof Array) {
// convert val from Array to object
let valToObj = {};
val.forEach((v, i) => {
valToObj[i] = v;
});
val = valToObj;
}
let newPrefex = prefex + key;
if (val instanceof Object) {
urlParams += toUrlParams(val, newPrefex + '-');
} else {
urlParams += newPrefex + '=' + val;
}
urlParams += '&';
}
// remove last &
urlParams = urlParams.slice(0, -1);
// return url params
return urlParams;
}
// encodeURI
return encodeURI(toUrlParams(obj));
}
// convert url params to obj
function urlParamsToObj(urlParams) {
// decodeURI
urlParams = decodeURI(urlParams);
let toObj = (urlParams) => {
let obj = {};
let urlParamsArr = urlParams.split('&');
let subUrlParramsObj = {};
// loop through urlParams
for (let i = 0; i < urlParamsArr.length; i++) {
let item = urlParamsArr[i];
// get key and value
let key = item.split('=')[0];
let val = item.split('=')[1] ?? null;
let keys = key.split('-');
if (val == "null") {
val = null;
} else if (val == "undefined") {
val = undefined;
} else if (val == "true") {
val = true;
} else if (val == "false") {
val = false;
} else if (val == "NaN") {
val = NaN;
} else if (val == "Infinity") {
val = Infinity;
}
// if keys length is 1 then set obj[key] to val
if (keys.length == 1) {
// check if obj contains key
if (obj.hasOwnProperty(key)) {
// if obj[key] is an array then push val
if (obj[key] instanceof Array) {
obj[key].push(val);
} else {
// create array and push val
obj[key] = [obj[key], val];
}
} else {
obj[key] = val;
}
}
// if keys length is 2 then set obj[keys[0]][keys[1]] to val
else if (keys.length > 1) {
let key0 = keys[0];
// check if subUrlParramsObj contains keys[0]
if (!subUrlParramsObj[key0]) {
subUrlParramsObj[key0] = [];
}
// remove keys[0] from keys
keys.shift();
// join keys with -
key = keys.join('-');
let param = key + '=' + val;
// add param to subUrlParramsObj[keys[0]]
subUrlParramsObj[key0].push(param);
}
}
// loop through subUrlParramsObj
for (let key in subUrlParramsObj) {
// join subUrlParramsObj[key] with &
let val = subUrlParramsObj[key].join('&');
// set obj[key] to val
obj[key] = toObj(val);
}
// return obj
return obj;
}
return checkIfObjShouldBeArrayAndConvert(toObj(urlParams));
}
// check if object should be converted to array, if its keys are numbers
function checkIfObjShouldBeArrayAndConvert(obj) {
// if obj is an array
if (obj instanceof Array) {
// loop through obj
obj.forEach((item, i) => {
// check if item is an object
if (item instanceof Object) {
// convert item to array
obj[i] = checkIfObjShouldBeArrayAndConvert(item);
}
});
// return obj
return obj;
}
// check if all keys are numbers
let canConvertToArray = true;
for (let key in obj) {
// get value
let val = obj[key];
// check if value is an object or Array
if (val instanceof Object || val instanceof Array) {
obj[key] = checkIfObjShouldBeArrayAndConvert(val);
}
if (isNaN(key)) {
canConvertToArray = false;
}
}
// order obj by keys
let orderedObj = {};
Object.keys(obj).sort().forEach(function(key) {
orderedObj[key] = obj[key];
});
// check if the first key is 0
if (Object.keys(orderedObj)[0] != 0) {
canConvertToArray = false;
}
// check if the keys step is 1
let keys = Object.keys(orderedObj);
// loop through keys
for (let i = 0; i < keys.length - 1; i++) {
// get key
let key = keys[i];
// get next key
let nextKey = keys[i + 1];
// get key step
let keyStep = nextKey - key;
// check if key step is 1
if (keyStep != 1) {
canConvertToArray = false;
break;
}
}
// if all keys are numbers then convert obj to array
if (canConvertToArray) {
let arr = [];
for (let key in orderedObj) {
arr.push(orderedObj[key]);
}
return arr;
}
// return obj
return obj;
}
// add params to url
function addParamsToUrl(params, url = window.location.href) {
// check if url has params
if (url.indexOf('?') == -1) {
url += '?';
} else {
url += '&';
}
return url + params ?? '';
}
function addObjToUrl(obj, url = window.location.href) {
return addParamsToUrl(objToUrlParams(obj), url);
}
// extract params from url
function extractParamsFromUrl(url = window.location.href) {
return urlParamsToObj(url.split('?')[1]);
}
// test
let urlParams = objToUrlParams({
a: 1,
b: "zad",
c: {
d: 2,
e: "f"
},
j: [1, 2, 3, 4]
});
console.log(urlParams); // a=1&b=zad&c-d=2&c-e=f&j=1&j=2&j=3&j=4
let obj = urlParamsToObj(urlParams);
console.log(obj); // { "a": "1", "b": "zad", "j": [ "1", "2", "3", "4" ], "c": { "d": "2", "e": "f" } }Check the parse_string function http://php.net/manual/en/function.parse-str.php
It will return all the variables from a query string, including arrays.
Example from php.net:
<?php
$str = "first=value&arr[]=foo+bar&arr[]=baz";
parse_str($str);
echo $first; // value
echo $arr[0]; // foo bar
echo $arr[1]; // baz
parse_str($str, $output);
echo $output['first']; // value
echo $output['arr'][0]; // foo bar
echo $output['arr'][1]; // baz
?>
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