I have the following javascript object literal (excerpt)
var foo = {"hello[35]":100,"goodbye[45]":42};
I have the following query:
var query = "hello"
I would like to call foo[query] to obtain the value 100, but there is a [35] for which I don't necessarily know the value of. I know for sure that I will get a unique match. Is there any way to input query is some kind of javascript regular expression? i.e.
Regex = /hello/
foo[Regex]
100
pardon the noob question...
What you have here:
var foo = {"hello[35]":100,"goodbye[45]":42};
is not JSON, which is a string representation of an object; what you have is an object literal, which creates an actual JavaScript object. As far as I know the only way to retrieve a value from an object by matching a property name with a regex is to enumerate the property names and test each one. The regex you'll need is something like:
/^hello(\[\d*\])?$/
...which will match against "hello" optionally followed by zero or more digits in square brackets. But you don't want to hard code "hello" given that you also (presumably) need the "goodbye" value, so use a function:
function getPropertyByRegex(obj,propName) {
var re = new RegExp("^" + propName + "(\\[\\d*\\])?$"),
key;
for (key in obj)
if (re.test(key))
return obj[key];
return null; // put your default "not found" return value here
}
var foo = {"hello[35]":100,"goodbye[45]":42};
alert(getPropertyByRegex(foo, "hello")); // 100
alert(getPropertyByRegex(foo, "goodbye")); // 42
alert(getPropertyByRegex(foo, "whatever")); // null (not found)
Demo: http://jsfiddle.net/asDQm/
Not sure if you can use regex without any plugins or so ...
This might help already ...
var foo = {"hello[35]":100,"goodbye[45]":42};
var query = "hello";
for(var key in foo){
if (key.indexOf(query) > -1)
document.write(foo[key]);
}
http://jsfiddle.net/3qqSr
I am noob here too but I have seen this page previously see it helps you with your question. It basically explains JSon path. Also see this question.
As your JSON is a string, you can use a regexp with this kind of statement:
var foo = '{"hello[35]":100,"goodbye[45]":42}';
var result = foo.match(/"hello\[\d*\]":\d*/g);
result = result[0].split(":")[1];
alert(result);
See it live on jsfiddle
Note that you could use a var instead of "hello" in your regexp.
var foo = {"hello[35]":100,"goodbye[45]":42};
foo = foo.replace(/\[\d+\]/g,'');
var obj = (new Function("return "+foo))();
obj.hello -> 100
obj.goodbye -> 42
var query = 'hello';
obj[query] -> 100
function getVal(s, q){
var r = s.match(new RegExp(q + "\\[\\d*\\]\":(\\d*)[\\,\\}]"));
return r?r.pop():false;
}
getVal(foo, "hello")
Related
I have a calculation string from a database like:
var calc = "{a}+{b}==2"
and I want to pull all the elements with "{}" so that I can look up their values from a database. What's the fastest way of doing this, so I end up with an ordered array that I can look up, and replace the values back in the string.
I've considered:
- For loop, looking for { then finding the next }
- Split with a map
- IndexOf
Using regex
var exp = /{([^}]+)}/g ,index;
while(index = exp.exec("{a}+{b}==2")) {
console.log(index[1]);
}
.
Demo
Not sure if it's the "fastest" way, but you should consider using a regex.
Something like:
var calc = "{a}+{b}==2";
var re = /{([^}]+)}/g;
var res;
var result = [];
while (res = re.exec(calc))
{
result.push(res[1]);
}
console.log(result);
Your regex may need to be refined based on the actual definition of the {} expressions (based on allowed characters, quoting, etc.).
Once you have received the values back, you can then use replace to replace the values.
var values = {a: 1, b: 3};
var replaced = calc.replace(re,function(match,name) { return values[name]; });
console.log(replaced);
NB: be very careful if you plan to then send this to eval or the like.
Regex comes to the mind first but one other way of implementing this job in O(n) time could be;
function getDatas(s){
var dataOn = false;
return Array.prototype.reduce.call(s,(d,c) => dataOn ? c !== "}" ? (d[d.length-1] += c,d)
: (dataOn = false, d)
: c === "{" ? (dataOn = true, d.push(""),d)
: d, []);
}
var calc = "{a}+{b}+{colorSpace}==2",
result = getDatas(calc);
console.log(result);
So out of curiosity i have done some tests on JSBen and it seems that #jcaron's regex is indeed much efficient. You may extend those tests with any of your other ideas like indexOf or for loop.
disclaimer - absolutely new to regexes....
I have a string like this:
subject=something||x-access-token=something
For this I need to extract two values. Subject and x-access-token.
As a starting point, I wanted to collect two strings: subject= and x-access-token=. For this here is what I did:
/[a-z,-]+=/g.exec(mystring)
It returns only one element subject=. I expected both of them. Where i am doing wrong?
The g modifier does not affect exec, because exec only returns the first match by specification. What you want is the match method:
mystring.match(/[a-z,-]+=/g)
No regex necessary. Write a tiny parser, it's easy.
function parseValues(str) {
var result = {};
str.split("||").forEach(function (item) {
var parts = item.split("=");
result[ parts[0] /* key */ ] = parts[1]; /* value */
});
return result;
}
usage
var obj = parseValues("subject=something||x-access-token=something-else");
// -> {subject: "something", x-access-token: "something-else"}
var subj = obj.subject;
// -> "something"
var token = obj["x-access-token"];
// -> "something-else"
Additional complications my arise when there is an escaping schema involved that allows you to have || inside a value, or when a value can contain an =.
You will hit these complications with regex approach as well, but with a parser-based approach they will be much easier to solve.
You have to execute exec twice to get 2 extracted strings.
According to MDN: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/exec
If your regular expression uses the "g" flag, you can use the exec() method multiple times to find successive matches in the same string.
Usually, people extract all strings matching the pattern one by one with a while loop. Please execute following code in browser console to see how it works.
var regex = /[a-z,-]+=/g;
var string = "subject=something||x-access-token=something";
while(matched = regex.exec(string)) console.log(matched);
You can convert the string into a valid JSON string, then parse it to retrieve an object containing the expected data.
var str = 'subject=something||x-access-token=something';
var obj = JSON.parse('{"' + str.replace(/=/g, '":"').replace(/\|\|/g, '","') + '"}');
console.log(obj);
I don't think you need regexp here, just use the javascript builtin function "split".
var s = "subject=something1||x-access-token=something2";
var r = s.split('||'); // r now is an array: ["subject=something1", "x-access-token=something2"]
var i;
for(i=0; i<r.length; i++){
// for each array's item, split again
r[i] = r[i].split('=');
}
At the end you have a matrix like the following:
y x 0 1
0 subject something1
1 x-access-token something2
And you can access the elements using x and y:
"subject" == r[0][0]
"x-access-token" == r[1][0]
"something2" == r[1][1]
If you really want to do it with a pure regexp:
var input = 'subject=something1||x-access-token=something2'
var m = /subject=(.*)\|\|x-access-token=(.*)/.exec(input)
var subject = m[1]
var xAccessToken = m[2]
console.log(subject);
console.log(xAccessToken);
However, it would probably be cleaner to split it instead:
console.log('subject=something||x-access-token=something'
.split(/\|\|/)
.map(function(a) {
a = a.split(/=/);
return { key: a[0], val: a[1] }
}));
I'm writing a JavaScript function to extract a segment out of a URL that appears to the right of a designated segment.
For instance, if this is my URL ...
mysite.com/cat/12/dog/34?test=123
... I would like to be able to pass 'cat' to the function and get 12, and later pass 'dog' to the function and have it return 34. I found this answer on StackOverflow to extract the URL segment, but it uses a string literal. And I'm having difficulty concatenating a passed in value.
jQuery to parse our a part of a url path
Here is my code. In this, rather than hard coding 'cat' into the pattern match, I would like to pass 'cat' into the segmentName parameter and have the regular expression match on that.
var url = "www.mysite.com/cat/12/dog/34?test=123";
alert(getNextSegmentAfterSegmentName(url, 'cat'));
function getNextSegmentAfterSegmentName(currentPath, segmentName) {
var nextSegment = "";
segmentName = segmentName.toLowerCase();
//var currentPath = window.location.pathname.toLowerCase();
if (currentPath.indexOf(segmentName) >= 0) {
var path = currentPath.split('?')[0]; // Strip querystring
// How do I concatenate segmentName into this?
var matches = path.match(/\/cat\/([^\/]+)/);
if (matches) {
nextSegment = matches[1];
}
}
return nextSegment;
}
Here is a jsfiddle example:
http://jsfiddle.net/Stormjack/2Ebsv/
Thanks for your help!
You need to create a RegExp object if you want to create regex using some string variable:
path.match(new RegExp("\/" + segmentName + "\/([^\/]+)"));
I´m really new to regex and I have been looking around to find an answer but either it dont work or I get some kind of error so I will try to ask the question and hopefulyl somebody can guide me through it :)
I have a string that can look like this:
str = "car[brand=saab][wheels=4]"
I have no idea if you can get several different matches directly or if you need different .match() but anyhow.
I need everything before the first [] in 1 variable.
Then i need saab in another, and 4 in a third.
.replace with a callback function is your tool of choice when parsing custom formats in javascript. Consider:
parse = function(s) {
var result = {};
s.replace(/^(\w+)|\[(.+?)=(.+?)\]/g, function($0, $1, $2, $3) {
result[$2 || "kind"] = $1 || $3;
});
return result;
}
Example:
str = "car[brand=saab][wheels=4][price=1234][morestuff=foobar]"
console.log(parse(str))
// {"kind":"car","brand":"saab","wheels":"4","price":"1234","morestuff":"foobar"}
You can use this regex:
([^\[]*)\[[^=]+=([^\]]*)\]\[[^=]+=([^\]]*)\]
You can then grap matching group #1, #2 and #3
Live Demo: http://www.rubular.com/r/XNZfHcMAp8
In Javascript:
str = 'car[brand=saab][wheels=4]';
console.log('match::' + str.match(/([^[]*)\[[^=]+=([^\]]*)\]\[[^=]+=([^\]]*)\]/));
I think this should work :
([^[]+)(?:\[[^=]+=([^\]]+)\])+
Explainations :
([^[]) First, you match everything that is not a [.
(?:...)+ Then, when you find it, you're starting repeting a pattern
\[[^=] Find everything that is not an =, and discard it.
([^\]]) Find everything that is not a ] and capture it.
/([^\[]+)\[brand=([^\]]+)\]\[wheels=(\d)\]/
Works.
Try it like
var result = "car[brand=saab][wheels=4]".match(/([^\[]+)\[brand=([^\]]+)\]\[wheels=(\d)\]/)
Result would be
[ "car[brand=saab][wheels=4]", "car", "saab", "4" ]
you could do it with match in one shot, and get an array back.
below lines were tested in chrome console:
str = "car[brand=saab][wheels=4]";
"car[brand=saab][wheels=4]"
str.match(/[^=[\]]+(?=[[\]])/g)
["car", "saab", "4"]
function getObject(str) {
var props = str.split(/\[(.*?)\]/g),
object = {};
if (props.length) {
object.name = props.shift();
while (props.length) {
var prop = props.shift().split("=");
if(prop.length == 2){
object[prop[0]] = prop[1];
}
}
}
return object;
}
console.log(getObject("car[brand=saab][wheels=4]"));
I have a string that and I am trying to extract the characters before the quote.
Example is extract the 14 from 14' - €14.99
I am using the follwing code to acheive this.
$menuItem.text().match(/[^']*/)[0]
My problem is that if the string is something like €0.88 I wish to get an empty string returned. However I get back the full string of €0.88.
What I am I doing wrong with the match?
This is the what you should use to split:
string.slice(0, string.indexOf("'"));
And then to handle your non existant value edge case:
function split(str) {
var i = str.indexOf("'");
if(i > 0)
return str.slice(0, i);
else
return "";
}
Demo on JsFiddle
Nobody seems to have presented what seems to me as the safest and most obvious option that covers each of the cases the OP asked about so I thought I'd offer this:
function getCharsBefore(str, chr) {
var index = str.indexOf(chr);
if (index != -1) {
return(str.substring(0, index));
}
return("");
}
try this
str.substring(0,str.indexOf("'"));
Here is an underscore mixin in coffescript
_.mixin
substrBefore : ->
[char, str] = arguments
return "" unless char?
fn = (s)-> s.substr(0,s.indexOf(char)+1)
return fn(str) if str?
fn
or if you prefer raw javascript : http://jsfiddle.net/snrobot/XsuQd/
You can use this to build a partial like:
var beforeQuote = _.substrBefore("'");
var hasQuote = beforeQuote("14' - €0.88"); // hasQuote = "14'"
var noQoute = beforeQuote("14 €0.88"); // noQuote = ""
Or just call it directly with your string
var beforeQuote = _.substrBefore("'", "14' - €0.88"); // beforeQuote = "14'"
I purposely chose to leave the search character in the results to match its complement mixin substrAfter (here is a demo: http://jsfiddle.net/snrobot/SEAZr/ ). The later mixin was written as a utility to parse url queries. In some cases I am just using location.search which returns a string with the leading ?.
I use "split":
let string = "one-two-three";
let um = string.split('-')[0];
let dois = string.split('-')[1];
let tres = string.split('-')[2];
document.write(tres) //three