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How to extract ID from string in Javascript

I got a string
var str = "javascript:DeleteCountryConfirm(191)";
and I need to have the ID 191 in a variable. How to do it?

In case it's actually a string like this:
var str = "javascript:DeleteCountryConfirm(191);"
You can do this:
var id = parseInt(str.match(/\d+/)[0], 10);
Or:
var id = parseInt(str.replace(/[^0-9-]/, ''), 10)

How to get particular string from one big string ?

I have string
var str = "Ahora MXN$1,709.05" and wanted to get only
"MXN$1,709.05" from this.
Can someone please help me?

You can use substring or replace. With replace you are going to replace something with nothing.
replace
var str = 'Ahora MXN$1,709.05';
var sub = 'Ahora ';
var res = str.replace(sub,'');
substring
var str = 'Ahora MXN$1,709.05';
var sub = 'Ahora ';
var res = str.substring(sub.length);
JsFiddle

You can use either substring or Regex
Using substring
var str = "Ahora MXN$1,709.05";
var result = str.substring('Ahora '.length);
console.log(result);
Using Regex
var str = "Ahora MXN$1,709.05";
var myRegexp = /Ahora\s(.*?)(?:\s|$)/g;
var match = myRegexp.exec(str);
console.log(match[1]);

JavaScript get character in sting after [ and before ]

I have some strings like:
str1 = "Point[A,B]"
str2 = "Segment[A,B]"
str3 = "Circle[C,D]"
str4 = "Point[Q,L]"
Now I want to have function that gives me character after "[" and the character before "]". How could I make something like that ?

try this one...
var str = "Point[A,B]";
var start_pos = str.indexOf('[') + 1;
var end_pos = str.indexOf(']',start_pos);
var text_to_get = str.substring(start_pos,end_pos)
alert(text_to_get);

You'd need regex to do that
var matches = /\[(.*?)\]/.exec(str1);
alert(matches[1]);

You can use match() to extract the characters:
str.match(/\[(.*)\]/)[1]
A safer way would be:
var matches = str.match(/\[(.*)\]/);
if(matches) {
var chars = matches[1];
}

Here's an approach which avoids regex.
var str = "Point[A,B]";
var afterOpenBracket = str.split("[")[1]; // returns "A,B]"
var bracketContents = afterOpenBracket.split("]")[0]; // returns "A,B"
There, pretty simple! bracketContents now contains the entirety of the text between the first set of brackets.
We can stop here, but I'll go a step further anyway and split up the parameters.
var parameters = bracketContents.split(","); // returns ["A", "B"]

Or in case u have more [A,C,D,B] and don't want to use regex:
var str1 = "Point[A,C,D,B]";
function extract(str1){
var a = str1.charAt(str1.indexOf('[')+1);
var b = str1.charAt(str1.indexOf(']')-1);
return [a, b];
//or
//a.concat(b); //to get a string with that values
}
console.log(extract(str1));

Find text between two characters and for each, do something

I have a file full with text in the following format:
(ignoring the fact that it is CSS) I need to get the string between the two | characters and each time, do something:
<div id="unused">
|#main|
#header|
.bananas|
#nav|
etc
</div>
The code I have is this:
var test_str = $('#unused').text();
var start_pos = test_str.indexOf('|') + 1;
var end_pos = test_str.indexOf('|',start_pos);
var text_to_get = test_str.substring(start_pos,end_pos);
//I want to do something with each string here
This just gets the first string. How can I add logic in there to do something for each string?

You can use split method to get array of strings between |
Live Demo
arr = $('#unused').text().split('|');

You can split like
var my_splitted_var = $('#unused').text().split('|');

One way;
$.each($("#unused").text().split("|"), function(ix, val) {
val = $.trim(val); //remove \r|\n
if (val !== "")
alert(val);
});

One way :
var test_str = $('#unused').text();
while(!test_str.indexOf('|'))
{
var start_pos = test_str.indexOf('|') + 1;
var end_pos = test_str.indexOf('|',start_pos);
var text_to_get = test_str.substring(start_pos,end_pos);
test_str = test_str.slice(end_pos,test_str.length);
}

RegExp-Version:
LIVE DEMO (jsfiddle.net)
var trimmedHtml = $("#unused").html().replace(/\s/g, '');
var result = new Array();
var regExp = /\|(.+?)(?=\|)/g;
var match = regExp.exec(trimmedHtml);
result.push(match[1]);
while (match != null) {
match = regExp.exec(trimmedHtml);
if (match != null) result.push(match[1]);
}
alert(result);
So you only get the elements BETWEEN the pipes (|).
In my example I pushed every matching result to an array. You can now iterate over it to get your result.

Looking for a regex to parse parameters string for JS

I cannot find out the regex to get param value from the part of query string:
I need to send parameter name to a method and get parameter value as result for string like
"p=1&qp=10".
I came up with the following:
function getParamValue(name) {
var regex_str = "[&]" + name + "=([^&]*)";
var regex = new RegExp(regex_str);
var results = regex.exec(my_query_string);
// check if result found and return results[1]
}
My regex_str now doesn't work if name = 'p'. if I change regex_str to
var regex_str = name + "=([^&]*)";
it can return value of param 'qp' for param name = 'p'
Can you help me with regex to search the beginning of param name from right after '&' OR from the beginning of a string?

This might work, depending on if you have separated the parameter part.
var regex_str = "(?:^|\&)" + name + "=([^&]*)";
or
var regex_str = "(?:\&|\?)" + name + "=([^&]*)";

Looks like split will work better here:
var paramsMap = {};
var params = string.split("&");
for (var i = 0; i < params.length; ++i) {
var keyValue = params[i].split("=", 2);
paramsMap[keyValue[0]] = keyValue[1];
}
If you desperately want to use a regex, you need to use the g flag and the exec method. Something along the lines of
var regex = /([^=]+)=([^&]+)&?/g;
var paramsMap = {};
while (true) {
var match = regex.exec(input);
if (!match)
break;
paramsMap[match[1]] = match[2];
}
Please note that since the regex object becomes stateful, you either need to reset its lastIndex property before running another extraction loop or use a new RegExp instance.

Change your regex string to the following:
//pass the query string and the name of the parameter's value you want to retrieve
function getParamValue(my_query_string , name)
{
var regex_str = "(?:^|\&)" + name + "\=([^&]*)";
var regex = new RegExp(regex_str);
var results = regex.exec(my_query_string);
try
{
if(results[1] != '')
{
return results[1];
}
}
catch(err){};
return false;
}