Catching a param from URL by using Node.js - javascript

I have a constant link looking like this:
http://link.com/?val1=val1&val2=val2
And this link redirects me to a new link with a random value of a constant param such like;
http://link2.com/?constant=randomvalue/
Each time I use the first link, I get a random value from the following link.
By using Node.js, how can I catch the 'randomvalue' of 'constant' in the second link?
I have to use the first link to reach the second one.

Try reading the second link as a URL
let secondURL = new URL("http://link2.com/?constant=randomvalue/");
Then extract the value of the constant searchparam like so
let constantValue = secondURL.searchParams.get("constant"); //"randomvalue/"

#Misantorp's answer is probably best, but there is another way to do it. Check out the querystring module built into Node, it has a convenient parse method just for things like this: https://nodejs.org/api/querystring.html
This should work:
const querystring = require('querystring');
querystring.parse("http://link2.com/?constant=randomvalue/"); // { 'http://link2.com/?constant': 'randomvalue/' }
You may want to substring from the ? onwards to make it more clear:
const str = "http://link2.com/?constant=randomvalue/";
const paramIndex = str.indexOf("?");
if (paramIndex >= 0) {
const queryParamStr = str.substr(str.indexOf("?"));
const queryParams = querystring.parse(queryParamStr);
console.log(queryParams["constant"]);
}

Related

How to Get 10 from this link (https://google.com/?ib=10)

Check this image
I have this link in (note this link not from search URL)
var link = https://google.com/?ib=10 in main.js file.
Now how to get that 10 from this link in javaScript on Page load
I have tried this way
var link1 = link;
const url3 = new URLSearchParams(link1);
const ur = url3.get("ib");
var finaltgid = ur;
alert(ur);
But its not working may be this code only work when we use window.location.search
Instead of var or const
urlsearchparams does not parse full url, you need to pass only query part, like this:
var link = 'https://google.com/?ib=10';
const url = new URLSearchParams(new URL(link).search);
const ib = url.get("ib");
console.log(ib);
URLSearchParams only accepts the actual query part in the constructor. You are including the full link.
Edit: For a given link you can just supply the link in place of document.location (which directly fetches the pages current location)
Considering this as Vanilla JS. You can do the following.
let params = (new URL(document.location)).searchParams;
let ib = parseInt(params.get('ib')); // is the number 10
Note, using the parseInt to get the value as a number.

Adding parameters to url on page load only if no paremeters already exist

I searched for the answer to my question and even tried some solutions, but wasn't able to get anything to really work. I'm newish to javascript, so that might also be why.
I have a specific URL and whenever someone goes to that URL, I want to add parameters to it, but only if no parameters are already present. Parameters get added to the URL for other on click events, but on page load, I need a set of parameters added to the URL.
I tried to use the history API and I think I'm kind of close, but I'm not able to get it to do what I want it to do.
function addDefaultParam(url) {
var currentURL = window.location.href; //get the current url
var baseURL = '/our-partners'; //this is the url that should have params added
var paramString = '?asc=true&sortBy=display_name'; //here are the params
if (currentURL === baseURL) {
window.history.pushState("object or string", "Title", "/" + paramString);
}
return url;
}
I'm using basic js in this because that's what was used in the other functions (I inherited this code). Any help would be greatly appreciated.
You can register the addDefaultParam function to fire when the document first loads in the browser and use the Location interface to check the state of the current path and query string of the URL and if they match your conditions, update the current query string value.
See below for an example:
window.addEventListener("load", addDefaultParam);
function addDefaultParam() {
let currentPath = document.location.pathname;
let currentQueryString = document.location.search;
let targetPath = "/our-partners";
if (currentPath === targetPath && !currentQueryString) {
document.location.search = "?asc=true&sortBy=display_name";
}
}

How to handle duplicate forward slashes on url

I'm using React and I'm trying to handle duplicate forward slashes on my website similar to Facebook. Its works like this:
If the user acess: https://facebook.com///settings the url is updated to https://facebook.com/settings
I'm trying to do this overriding the window.location.pathname like this:
const pattern = /\/+[/]/;
const urlFinal = window.location.pathname.replace(pattern, "");
window.location.pathname = urlFinal;
But it returns an infinite loop of refresh on the window.
So, how can I do that? Someone can help me?
You need to leave a slash:
let pathName = window.location.pathname;
const pattern = /\/+[/]/;
const urlFinal = pathname.replace(pattern, "/");
if (urlFinal.length < pathName) window.location.pathname = urlFinal;

JS: get hostname from url , regex not working

I am trying to get hostname from set of urls that my webapp can encounter with.
The desired output should be something like http://localhost/Webapp/, ending at /Webapp/ and everything after that should be removed.
Kindly note that I dont want to use word Webapp in regex as this name is dynamic and used for demo/testcase only.this can be anything , not harcoded.
In real example I am using location.href.replace(/index.+/g, "").replace(/#.+/g, "")
and I want to keep only hostname ending atWebapp/.
Problem:
my solution seems to working fine except "http://localhost/Webapp/#" is not working correctly ? why is that ? see fiddle below
JSFIDDLE: http://jsfiddle.net/bababalcksheep/um0uqb8v/
JS:
var getHost = function (url) {
return url.replace(/index.+/g, "").replace(/#.+/g, "")
};
var urls = [
"http://localhost/Webapp/",
"http://localhost/Webapp/#",
"http://localhost:8080/Webapp/#sdf#dfgdf#fdg",
"12.168.1.1:8080/Webapp/index.html#",
"https://localhost/Webapp/index.html#ab#bg",
"https://localhost/Webapp/index.html"
];
//Print all urls
$.each(urls, function () {
$("<p/>").text(getHost(this)).appendTo($(".test"));
});
Use url.match(/https?:\/\/([^\/]+)/);
EDIT:
It returns an array where the 1st element is the host with protocol and the 2nd without.
You can try removing anything after the last slash (files and hash-es):
var getHost = function (url) {
return url.replace(/\/[^/]*?$/, '/');
};
And here's the updated fiddle.
There's a bit of a trick you can use to get the browser to extract the hostname for you.
var getHost = function (url) {
var a = document.createElement('a');
a.href = url;
return a.hostname;
};
It also appears you want the path as well. You can access it with the pathname property of the a element. If you're doing that, you ought to rename the function to something like getHostAndPath().

Passing parameters to JavaScript files

Often I will have a JavaScript file that I want to use which requires certain variables be defined in my web page.
So the code is something like this:
<script type="text/javascript" src="file.js"></script>
<script type="text/javascript">
var obj1 = "somevalue";
</script>
But what I want to do is:
<script type="text/javascript"
src="file.js?obj1=somevalue&obj2=someothervalue"></script>
I tried different methods and the best one yet is to parse the query string like this:
var scriptSrc = document.getElementById("myscript").src.toLowerCase();
And then search for my values.
I wonder if there is another way to do this without building a function to parse my string.
Do you all know other methods?
I'd recommend not using global variables if possible. Use a namespace and OOP to pass your arguments through to an object.
This code belongs in file.js:
var MYLIBRARY = MYLIBRARY || (function(){
var _args = {}; // private
return {
init : function(Args) {
_args = Args;
// some other initialising
},
helloWorld : function() {
alert('Hello World! -' + _args[0]);
}
};
}());
And in your html file:
<script type="text/javascript" src="file.js"></script>
<script type="text/javascript">
MYLIBRARY.init(["somevalue", 1, "controlId"]);
MYLIBRARY.helloWorld();
</script>
You can pass parameters with arbitrary attributes. This works in all recent browsers.
<script type="text/javascript" data-my_var_1="some_val_1" data-my_var_2="some_val_2" src="/js/somefile.js"></script>
Inside somefile.js you can get passed variables values this way:
........
var this_js_script = $('script[src*=somefile]'); // or better regexp to get the file name..
var my_var_1 = this_js_script.attr('data-my_var_1');
if (typeof my_var_1 === "undefined" ) {
var my_var_1 = 'some_default_value';
}
alert(my_var_1); // to view the variable value
var my_var_2 = this_js_script.attr('data-my_var_2');
if (typeof my_var_2 === "undefined" ) {
var my_var_2 = 'some_default_value';
}
alert(my_var_2); // to view the variable value
...etc...
Another idea I came across was assigning an id to the <script> element and passing the arguments as data-* attributes. The resulting <script> tag would look something like this:
<script id="helper" data-name="helper" src="helper.js"></script>
The script could then use the id to programmatically locate itself and parse the arguments. Given the previous <script> tag, the name could be retrieved like this:
var name = document.getElementById("helper").getAttribute("data-name");
We get name = helper
Check out this URL. It is working perfectly for the requirement.
http://feather.elektrum.org/book/src.html
Thanks a lot to the author. For quick reference I pasted the main logic below:
var scripts = document.getElementsByTagName('script');
var myScript = scripts[ scripts.length - 1 ];
var queryString = myScript.src.replace(/^[^\?]+\??/,'');
var params = parseQuery( queryString );
function parseQuery ( query ) {
var Params = new Object ();
if ( ! query ) return Params; // return empty object
var Pairs = query.split(/[;&]/);
for ( var i = 0; i < Pairs.length; i++ ) {
var KeyVal = Pairs[i].split('=');
if ( ! KeyVal || KeyVal.length != 2 ) continue;
var key = unescape( KeyVal[0] );
var val = unescape( KeyVal[1] );
val = val.replace(/\+/g, ' ');
Params[key] = val;
}
return Params;
}
You use Global variables :-D.
Like this:
<script type="text/javascript">
var obj1 = "somevalue";
var obj2 = "someothervalue";
</script>
<script type="text/javascript" src="file.js"></script">
The JavaScript code in 'file.js' can access to obj1 and obj2 without problem.
EDIT Just want to add that if 'file.js' wants to check if obj1 and obj2 have even been declared you can use the following function.
function IsDefined($Name) {
return (window[$Name] != undefined);
}
Hope this helps.
Here is a very rushed proof of concept.
I'm sure there are at least 2 places where there can be improvements, and I'm also sure that this would not survive long in the wild. Any feedback to make it more presentable or usable is welcome.
The key is setting an id for your script element. The only catch is that this means you can only call the script once since it looks for that ID to pull the query string. This could be fixed if, instead, the script loops through all query elements to see if any of them point to it, and if so, uses the last instance of such an script element. Anyway, on with the code:
Script being called:
window.onload = function() {
//Notice that both possible parameters are pre-defined.
//Which is probably not required if using proper object notation
//in query string, or if variable-variables are possible in js.
var header;
var text;
//script gets the src attribute based on ID of page's script element:
var requestURL = document.getElementById("myScript").getAttribute("src");
//next use substring() to get querystring part of src
var queryString = requestURL.substring(requestURL.indexOf("?") + 1, requestURL.length);
//Next split the querystring into array
var params = queryString.split("&");
//Next loop through params
for(var i = 0; i < params.length; i++){
var name = params[i].substring(0,params[i].indexOf("="));
var value = params[i].substring(params[i].indexOf("=") + 1, params[i].length);
//Test if value is a number. If not, wrap value with quotes:
if(isNaN(parseInt(value))) {
params[i] = params[i].replace(value, "'" + value + "'");
}
// Finally, use eval to set values of pre-defined variables:
eval(params[i]);
}
//Output to test that it worked:
document.getElementById("docTitle").innerHTML = header;
document.getElementById("docText").innerHTML = text;
};
Script called via following page:
<script id="myScript" type="text/javascript"
src="test.js?header=Test Page&text=This Works"></script>
<h1 id="docTitle"></h1>
<p id="docText"></p>
might be very simple
for example
<script src="js/myscript.js?id=123"></script>
<script>
var queryString = $("script[src*='js/myscript.js']").attr('src').split('?')[1];
</script>
You can then convert query string into json like below
var json = $.parseJSON('{"'
+ queryString.replace(/&/g, '","').replace(/=/g, '":"')
+ '"}');
and then can use like
console.log(json.id);
This can be easily done if you are using some Javascript framework like jQuery.
Like so,
var x = $('script:first').attr('src'); //Fetch the source in the first script tag
var params = x.split('?')[1]; //Get the params
Now you can use these params by splitting as your variable parameters.
The same process can be done without any framework but will take some more lines of code.
Well, you could have the javascript file being built by any of the scripting languages, injecting your variables into the file on every request. You would have to tell your webserver to not dish out js-files statically (using mod_rewrite would suffice).
Be aware though that you lose any caching of these js-files as they are altered constantly.
Bye.
HTML:
<script src='greet.js' data-param1='hello' data-param2='world'></script>
// greet.js:
const prm1=document.currentScript.dataset.param1;
const prm2=document.currentScript.dataset.param2;
Nice question and creative answers but my suggetion is to make your methods paramterized and that should solve all your problems without any tricks.
if you have function:
function A()
{
var val = external_value_from_query_string_or_global_param;
}
you can change this to:
function B(function_param)
{
var val = function_param;
}
I think this is most natural approach, you don't need to crate extra documentation about 'file parameters' and you receive the same. This specially useful if you allow other developers to use your js file.
It's not valid html (I don't think) but it seems to work if you create a custom attribute for the script tag in your webpage:
<script id="myScript" myCustomAttribute="some value" ....>
Then access the custom attribute in the javascript:
var myVar = document.getElementById( "myScript" ).getAttribute( "myCustomAttribute" );
Not sure if this is better or worse than parsing the script source string.
Here i have found an another way of doing this same thing. In the reuired js file [cttricks.js as i have used it for testing, you can have your any .js file], we'll simply list up all script elements and get the required one as it is always going to be at last index. And then get ".attributes.src.value" from that.
Now, in any case of script call, it is
<script src="./cttricks.js?data1=Hello&data2=World"></script>
And in the cttricks.js script file,
var scripts = document.getElementsByTagName('script');
var jsFile = new URL("http://" + scripts[scripts.length-1].attributes.src.value);
/*get value from query parameters*/
console.log(jsFile.searchParams.get("data1"));
console.log(jsFile.searchParams.get("data2"));
Enjoy!!
No, you cant really do this by adding variables to the querystring portion of the JS file URL. If its writing the portion of code to parse the string that bothers you, perhaps another way would be to json encode your variables and put them in something like the rel attribute of the tag? I don't know how valid this is in terms of HTML validation, if thats something you're very worried about. Then you just need to find the rel attribute of the script and then json_decode that.
eg
<script type='text/javascript' src='file.js' rel='{"myvar":"somevalue","anothervar":"anothervalue"}'></script>
If you need a way that passes CSP check (which prohibits unsafe-inline) then you have to use nonce method to add a unique value to both the script and the CSP directive or write your values into the html and read them again.
Nonce method for express.js:
const uuidv4 = require('uuid/v4')
app.use(function (req, res, next) {
res.locals.nonce = uuidv4()
next()
})
app.use(csp({
directives: {
scriptSrc: [
"'self'",
(req, res) => `'nonce-${res.locals.nonce}'` // 'nonce-614d9122-d5b0-4760-aecf-3a5d17cf0ac9'
]
}
}))
app.use(function (req, res) {
res.end(`<script nonce="${res.locals.nonce}">alert(1 + 1);</script>`)
})
or write values to html method. in this case using Jquery:
<div id="account" data-email="{{user.email}}"></div>
...
$(document).ready(() => {
globalThis.EMAIL = $('#account').data('email');
}
Although this question has been asked a while ago, it is still relevant as of today. This is not a trivial approach using script file params, but I already had some extreme use-cases that this way was most suited.
I came across this post to find out a better solution than I wrote a while ago, with hope to find maybe a native feature or something similar.
I will share my solution, up until a better one will be implemented. This works on most modern browsers, maybe even on older ones, didn't try.
All the solutions above, are based on the fact that it has to be injected with predefined and well marked SCRIPT tag and rely completely on the HTML implementation. But, what if the script is injected dynamically, or even worse, what if you are write a library, that will be used in a variety of websites?
In these and some other cases, all the above answers are not sufficient and even becoming too complicated.
First, let's try to understand what do we need to achieve here. All we need to do is to get the URL of the script itself, from there it's a piece of cake.
There is actually a nice trick to get the script URL from the script itself. One of the functionalities of the native Error class, is the ability to provide a stack trace of the "problematic location", including the exact file trace to the last call. In order to achieve this, I will use the stack property of the Error instance, that once created, will give the full stack trace.
Here is how the magic works:
// The pattern to split each row in the stack trace string
const STACK_TRACE_SPLIT_PATTERN = /(?:Error)?\n(?:\s*at\s+)?/;
// For browsers, like Chrome, IE, Edge and more.
const STACK_TRACE_ROW_PATTERN1 = /^.+?\s\((.+?):\d+:\d+\)$/;
// For browsers, like Firefox, Safari, some variants of Chrome and maybe other browsers.
const STACK_TRACE_ROW_PATTERN2 = /^(?:.*?#)?(.*?):\d+(?::\d+)?$/;
const getFileParams = () => {
const stack = new Error().stack;
const row = stack.split(STACK_TRACE_SPLIT_PATTERN, 2)[1];
const [, url] = row.match(STACK_TRACE_ROW_PATTERN1) || row.match(STACK_TRACE_ROW_PATTERN2) || [];
if (!url) {
console.warn("Something went wrong. You should debug it and find out why.");
return;
}
try {
const urlObj = new URL(url);
return urlObj.searchParams; // This feature doesn't exists in IE, in this case you should use urlObj.search and handle the query parsing by yourself.
} catch (e) {
console.warn(`The URL '${url}' is not valid.`);
}
}
Now, in any case of script call, like in the OP case:
<script type="text/javascript" src="file.js?obj1=somevalue&obj2=someothervalue"></script>
In the file.js script, you can now do:
const params = getFileParams();
console.log(params.get('obj2'));
// Prints: someothervalue
This will also work with RequireJS and other dynamically injected file scripts.
I think it is far more better and modern solution to just use localStorage on the page where the javascript is included and then just re-use it inside the javascript itself. Set it in localStorage with:
localStorage.setItem("nameOfVariable", "some text value");
and refer to it inside javascript file like:
localStorage.getItem("nameOfVariable");
It's possible to pass parameters to js modules and read them after via import.meta.url.
For example, with the following HTML
<script type="module">
import './index.mjs?someURLInfo=5';
</script>
the following JavaScript file will log the someURLInfo parameter:
// index.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5
The same applies when a file imports another:
// index.mjs
import './index2.mjs?someURLInfo=5';
// index2.mjs
new URL(import.meta.url).searchParams.get('someURLInfo'); // 5

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