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Why does RegExp exec() not work properly in my case? [duplicate]

This question already has answers here:
Why does a RegExp with global flag give wrong results?
(7 answers)
Closed 3 years ago.
If the RegExp is defined global and I use the vals array like I do, the result of exec will be the same everytime, so the code below is an infinity loop.
var regex = RegExp(/<(.*?)>.*?<\/\1>/, "g");
function readXml(xmlString) {
var obj = {};
var vals;
for (var i = 0;
(vals = regex.exec(xmlString)) !== null; i++) {
if (!obj[vals[1]]) obj[vals[1]] = [];
obj[vals[1]].push(readXml(vals[0].slice(vals[1].length + 1, -vals[1] - length - 3)));
}
if (i == 0) return xmlString;
return obj;
}
console.log(readXml("<a>a</a><b>b</b>"));
If the RegExp is defined in function, the result of exec will be the next match everytime, so the code below logs a and b.
function readXml(xmlString) {
var regex = RegExp(/<(.*?)>.*?<\/\1>/, "g");
var obj = {};
var vals;
for (var i = 0;
(vals = regex.exec(xmlString)) !== null; i++) {
if (!obj[vals[1]]) obj[vals[1]] = [];
obj[vals[1]].push(readXml(vals[0].slice(vals[1].length + 1, -vals[1] - length - 3)));
}
if (i == 0) return xmlString;
return obj;
}
console.log(readXml("<a>a</a><b>b</b>"));
If I do something else with vals arrray in the loop, the result of exec will be the next match everytime, so the code below logs an empty object.
var regex = RegExp(/<(.*?)>.*?<\/\1>/, "g");
function readXml(xmlString) {
var obj = {};
var vals;
for (var i = 0;
(vals = regex.exec(xmlString)) !== null; i++) {
vals = [2]
}
if (i == 0) return xmlString;
return obj;
}
console.log(readXml("<a>a</a><b>b</b>"));
I think it should be an object with a and b in the first case too.
Why doesn't it just do the same thing in all cases?

Global regexes (ie. using the g flag) keep track of the position of the last match in order to successfully get the next one the next time you call exec. It makes the assumption that you're passing the same input string each time, but if you go and change the input then it goes weird.
const regex = RegExp(/./,'g'); // should match each character, one at a time.
let input1 = 'test', match;
match = regex.exec(input1);
console.log(match[0]);
// now let's "re-use" the regex object...
let input2 = 'another test';
match = regex.exec(input2);
console.log(match[0]);
console.log("Where did the `a` go??");
You can access and modify the property responsible for this behaviour via regex.lastIndex, although in this case your best solution is to create a new RegExp object within the function, since you're working recursively.

Javascript pull data from string?

I have a long URL that contains some data that I need to pull. I am able to get the end of the URL by doing this:
var data = window.location.hash;
When I do alert(data); I receive a long string like this:
#access_token=0u2389ruq892hqjru3h289r3u892ru3892r32235423&token_type=Bearer&expires_in=3600
note in the example the access token is not valid, just random numbers I input for example purpose
Now that I have that long string stored in a variable, how can I parse out just the access token value, so everything in between the first '=' and '&. So this is what I need out of the string:
0u2389ruq892hqjru3h289r3u892ru3892r32235423
I was reading up on php explode, and others java script specific stuff like strip but couldn't get them to function as needed. Thanks guys.

DEMO (look in your debug console)
You will want to split the string by the token '&' first to get your key/value pairs:
var kvpairs = document.location.hash.substring(1).split('&');
Then, you will want to split each kvpair into a key and a value:
for (var i = 0; i < kvpairs.length; i++) {
var kvpair = kvpairs[i].split('=');
var k = kvpair[0];
var v = kvpair[1];
if (k != 'access_token')
continue;
console.log(v); //Here's your access token.
}
Here is a version wrapped into a function that you can use easily:
function getParam(hash, key) {
var kvpairs = hash.substring(1).split('&');
for (var i = 0; i < kvpairs.length; i++) {
var kvpair = kvpairs[i].split('=');
var k = kvpair[0];
var v = kvpair[1];
if (k != key)
continue;
return v;
}
return null;
}
Usage:
getParam(document.location.hash, 'access_token');

data.split("&")[0].split("=")[1]

var str = "#access_token=0u2389ruq892hqjru3h289r3u892ru3892r32235423&token_type=Bearer&expires_in=3600";
var requiredValue = str.split('&')[0].split('=')[1];

I'd use regex in case value=key pair changes position
var data = "#token_type=Bearer&access_token=0u2389ruq892hqjru3h289r3u892ru3892r32235423&expires_in=3600";
RegExp("access_token=([A-Za-z0-9]*)&").exec(data)[1];
output
"0u2389ruq892hqjru3h289r3u892ru3892r32235423"

Looks like I'm a bit late on this. Here's my attempt at a version that parses URL parameters into a map and gets any param by name.
var str = "#access_token=0u2389ruq892hqjru3h289r3u892ru3892r32235423&token_type=Bearer&expires_in=3600";
function urlToMap(url){
var startIndex = Math.max(url.lastIndexOf("#"), url.lastIndexOf("?"));
url = url.substr(startIndex+1);
var result = {};
url.split("&").forEach(function(pair){
var x = pair.split("=");
result[x[0]]=x[1];
});
return result;
}
function getParam(url, name){
return urlToMap(url)[name];
}
console.log(getParam(str, "access_token"));

To answer to your question directly (what's between this and that), you would need to use indexOf and substring functions.
Here's a little piece of code for you.
function whatsBetween (_strToSearch, _leftText, _rightText) {
var leftPos = _strToSearch.indexOf(_leftText) + _leftText.length;
var rightPos = _strToSearch.indexOf(_rightText, leftPos);
if (leftPos >= 0 && leftPos < rightPos)
return _strToSearch.substring(leftPos, rightPos);
return "";
}
Usage:
alert(whatsBetween, data,"=","#");
That said, I'd rather go with a function like crush's...

try this
var data = window.location.hash;
var d1 = Array();
d1 = data.split("&")
var myFilteredData = Array();
for( var i=0;i<d1.length;i++ )
{
var d2 = d1[i].split("=");
myFilteredData.push(d2[1]); //Taking String after '='
}
I hope it helps you.

Determine token value by comparing with token replaced string

I have a tokenised string like so;
var route = a/b/{firstId}/c/d/{nextId}
and I am wondering if it is possible with regex to get the value of "firstId" via a second string with tokens already replaced.
Example, if I have a given string;
var partPath = a/b/33
I can do something like;
function getValueFromPath(path, route){
//regex stuff
return tokenValue; //Expected result 33
}
getValueFromPath(partPath, route);
Thank you,
C.

A regex solution would be overly complicated (if you didn't define the route with a regexp right away). I'd just use
function getValueFromPath(path, route){
var actualParts = path.split("/"),
expectedParts = route.split("/"),
result = {};
for (var i=0; i<expectedParts.length; i++) {
if (i >= actualParts.length)
return result;
var actual = actualParts[i],
expected = expectedParts[i];
if (/^\{.+\}$/.test(expected))
result[ expected.slice(1, -1) ] = actual;
else if (actual != expected)
// non-matching literals found, abort
return result;
}
return result;
}
> getValueFromPath("a/b/33", "a/b/{firstId}/c/d/{nextId}")
{firstId: "33"}
> getValueFromPath("a/b/33/c/d/42/x", "a/b/{firstId}/c/d/{nextId}")
{firstId: "33", nextId: "42"}
Here's the same thing with "regex stuff" (notice that regex special characters in the route are not escaped, you have to take care about that yourself):
function getValueFromPath(path, route){
var keys = [];
route = "^"+route.split("/").reduceRight(function(m, part) {
return part + "(?:/" + m + ")?"; // make right parts optional
}).replace(/\{([^\/{}]+)\}/g, function(m, k) {
keys.push(k); // for every "variable"
return "([^/]+)"; // create a capturing group
});
var regex = new RegExp(route); // build an ugly regex:
// regex == /^a(?:\/b(?:\/([^/]+)(?:\/c(?:\/d(?:\/([^/]+))?)?)?)?)?/
var m = path.match(regex),
result = {};
for (var i=0; m && i<keys.length; i++)
result[keys[i]] = m[i+1];
return result;
}

You can create a regexp like this:
function getValueFromPath(path, route){
tokenValue = path.match(route)[1];
return tokenValue; //Expected result 33
}
var route = /\/a\/b\/([^\/]+)(\/c\/d\/([^\/]+))?/;
var partPath = '/a/b/33';
getValueFromPath(partPath, route); // == 33
http://jsfiddle.net/firstclown/YYvvn/2/
This will let you extract the first value at the first match with [1] and you can get the nextId by changing that to [3] (since [2] will give you the whole path after the 33).

How to get the query string by javascript?

How to extract the query string from the URL in javascript?
Thank you!

You can easily build a dictionary style collection...
function getQueryStrings() {
var assoc = {};
var decode = function (s) { return decodeURIComponent(s.replace(/\+/g, " ")); };
var queryString = location.search.substring(1);
var keyValues = queryString.split('&');
for(var i in keyValues) {
var key = keyValues[i].split('=');
if (key.length > 1) {
assoc[decode(key[0])] = decode(key[1]);
}
}
return assoc;
}
And use it like this...
var qs = getQueryStrings();
var myParam = qs["myParam"];

If you're referring to the URL in the address bar, then
window.location.search
will give you just the query string part. Note that this includes the question mark at the beginning.
If you're referring to any random URL stored in (e.g.) a string, you can get at the query string by taking a substring beginning at the index of the first question mark by doing something like:
url.substring(url.indexOf("?"))
That assumes that any question marks in the fragment part of the URL have been properly encoded. If there's a target at the end (i.e., a # followed by the id of a DOM element) it'll include that too.

Here's the method I use...
function Querystring() {
var q = window.location.search.substr(1), qs = {};
if (q.length) {
var keys = q.split("&"), k, kv, key, val, v;
for (k = keys.length; k--; ) {
kv = keys[k].split("=");
key = kv[0];
val = decodeURIComponent(kv[1]);
if (qs[key] === undefined) {
qs[key] = val;
} else {
v = qs[key];
if (v.constructor != Array) {
qs[key] = [];
qs[key].push(v);
}
qs[key].push(val);
}
}
}
return qs;
}
It returns an object of strings and arrays and seems to work quite well.
(Strings for single keys, arrays for the same key with multiple values.)

You need to simple use following function.
function GetQueryStringByParameter(name) {
name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
var regex = new RegExp("[\\?&]" + name + "=([^&#]*)"),
results = regex.exec(location.search);
return results == null ? "" : decodeURIComponent(results[1].replace(/\+/g, " "));
}
--- How to Use ---
var QueryString= GetQueryStringByParameter('QueryString');

Very Straightforward!
function parseQueryString(){
var assoc = {};
var keyValues = location.search.slice(1).split('&');
var decode = function(s){
return decodeURIComponent(s.replace(/\+/g, ' '));
};
for (var i = 0; i < keyValues.length; ++i) {
var key = keyValues[i].split('=');
if (1 < key.length) {
assoc[decode(key[0])] = decode(key[1]);
}
}
return assoc;
}

There is a new API called URLSearchParams in browsers which allow you to extract and change the values of the query string.
Currently, it seems to be supported in Firefox 44+, Chrome 49+ and Opera 36+.
Initialize/Input
To get started, create a new URLSearchParams object. For current implementations, you need to remove the "?" at the beginning of the query string, using slice(1) on the querystring, as Jake Archibald suggests:
var params = new URLSearchParams(window.location.search.slice(1)); // myParam=12
In later implementations, you should be able to use it without slice:
var params = new URLSearchParams(window.location.search); // myParam=12
Get
You can get params from it via the .get method:
params.get('myParam'); // 12
Set
Params can be changed using .set:
params.set('myParam', 'newValue');
Output
And if the current querystring is needed again, the .toString method provides it:
params.toString(); // myParam=newValue
There are a host of other methods in this API.
Polyfill
As browser support is still pretty thin, there is a small polyfill by Andrea Giammarchi (<3kB).

Works for me-
function querySt(Key) {
var url = window.location.href;
KeysValues = url.split(/[\?&]+/);
for (i = 0; i < KeysValues.length; i++) {
KeyValue= KeysValues[i].split("=");
if (KeyValue[0] == Key) {
return KeyValue[1];
}
}
}
function GetQString(Key) {
if (querySt(Key)) {
var value = querySt(Key);
return value;
}
}

You can use this Javascript :
function getParameterByName(name) {
var match = RegExp('[?&]' + name + '=([^&]*)').exec(window.location.search);
return match && decodeURIComponent(match[1].replace(/\+/g, ' '));
}
OR
You can also use the plugin jQuery-URL-Parser allows to retrieve all parts of URL, including anchor, host, etc.
Usage is very simple and cool:
$.url().param("itemID")
via James&Alfa

I have use this method
function getString()
{
var vars = [], hash;
var hashes = window.location.href.slice(window.location.href.indexOf('?') + 1).split('&');
for(var i = 0; i < hashes.length; i++)
{
hash = hashes[i].split('=');
vars.push(hash[0]);
vars[hash[0]] = hash[1];
}
return vars;
}
var buisnessArea = getString();

// Assuming "?post=1234&action=edit"
var urlParams = new URLSearchParams(window.location.search);
console.log(urlParams.has('post')); // true
console.log(urlParams.get('action')); // "edit"
console.log(urlParams.getAll('action')); // ["edit"]
console.log(urlParams.toString()); // "?post=1234&action=edit"
console.log(urlParams.append('active', '1')); // "?post=1234&action=edit&active=1"

Javascript token replace/append

I have a string that looks something like the following 'test:1;hello:five;just:23'. With this string I need to be able to do the following.
....
var test = MergeTokens('test:1;hello:five;just:23', 'yes:23;test:567');
...
The end result should be 'test:567;hello:five;just:23;yes:23' (note the exact order of the tokens is not that important).
Just wondering if anyone has any smart ideas of how to go about this. I was thinking a regex replace on each of the tokens on right and if a replace didn't occur because there was not match just append it. But maybe there is better way.
Cheers
Anthony
Edit: The right side should override the left. The left being what was originally there and the right side being the new content. Another way of looking at it, is that you only keep the tokens on the left if they don't exist on the right and you keep all the tokens on the right.
#Ferdinand
Thanks for the reply. The problem is the efficiency with which the solution you proposed. I was initially thinking down similar lines but discounted it due to the O(n*z) complexity of the merge (where n and z is the number tokens on the left and right respectively) let alone the splitting and joining.
Hence why I was trying to look down the path of a regex. Maybe behind the scenes, regex is just as bad or worse, but having a regex which removes any token from the left string that exists on the right (O(n) for the total amount of token on the right) and then just add the 2 string together (i.e. vat test = test1 + test2) seems more efficient. thanks

I would use join() and split() to create some utility functions to pack and unpack your token data to an object:
// Unpacks a token string into an object.
function splitTokens(str) {
var data = {}, pairs = str.split(';');
for (var i = 0; i < pairs.length; ++i) {
var pair = pairs[i].split(':');
data[pair[0]] = pair[1];
}
return data;
}
// Packs an object into a token string.
function joinTokens(data) {
var pairs = [];
for (var key in data) {
pairs.push(key + ":" + data[key]);
}
return pairs.join(';');
}
Using these, merging is easy:
// Merges all token strings (supports a variable number of arguments).
function mergeTokens() {
var data = {};
for (var i = 0; i < arguments.length; ++i) {
var d = splitTokens(arguments[i]);
for (var key in d) {
data[key] = d[key];
}
}
return joinTokens(data);
}
The utility functions are also useful if you want to extract some keys (say,"test") and/or check for existence:
var data = splitTokens(str);
if (data["test"] === undefined) {
// Does not exist
} else {
alert("Value of 'test': " + data["test"]);
}

The following is what I ended thiking about. What do you guys recon?
Thanks
Anthony
function Tokenizer(input, tokenSpacer, tokenValueSpacer) {
this.Tokenizer = {};
this.TokenSpacer = tokenSpacer;
this.TokenValueSpacer = tokenValueSpacer;
if (input) {
var TokenizerParts = input.split(this.TokenSpacer);
var i, nv;
for (i = 0; i < TokenizerParts.length; i++) {
nv = TokenizerParts[i].split(this.TokenValueSpacer);
this.Tokenizer[nv[0]] = nv[1];
}
}
}
Tokenizer.prototype.add = function(name, value) {
if (arguments.length == 1 && arguments[0].constructor == Object) {
this.addMany(arguments[0]);
return;
}
this.Tokenizer[name] = value;
}
Tokenizer.prototype.addMany = function(newValues) {
for (nv in newValues) {
this.Tokenizer[nv] = newValues[nv];
}
}
Tokenizer.prototype.remove = function(name) {
if (arguments.length == 1 && arguments[0].constructor == Array) {
this.removeMany(arguments[0]);
return;
}
delete this.Tokenizer[name];
}
Tokenizer.prototype.removeMany = function(deleteNames) {
var i;
for (i = 0; i < deleteNames.length; i++) {
delete this.Tokenizer[deleteNames[i]];
}
}
Tokenizer.prototype.MergeTokenizers = function(newTokenizer) {
this.addMany(newTokenizer.Tokenizer);
}
Tokenizer.prototype.getTokenString = function() {
var nv, q = [];
for (nv in this.Tokenizer) {
q[q.length] = nv + this.TokenValueSpacer + this.Tokenizer[nv];
}
return q.join(this.TokenSpacer);
}
Tokenizer.prototype.toString = Tokenizer.prototype.getTokenString;

i am a few years late, but i think this is what you are looking for:
function MergeTokens(input, replace){
var replaceTokens = replace.split(";");
for(i=0; i<replaceTokens.length; i++){
var pair = replaceTokens[i].split(":");
var result = input;
regString = "\\b" + pair[0] + ":[\\w]*\\b";
var reg = new RegExp(regString);
if(reg.test(result)){
result = result.replace(reg, replaceTokens[i]);
}
else{
result = result + replaceTokens[i];
}
}
return result;
}