Develop Reference

Split the date! (It's a string actually)

I want to split this kind of String :
"14:30 - 19:30" or "14:30-19:30"
inside a javascript array like ["14:30", "19:30"]
so I have my variable
var stringa = "14:30 - 19:30";
var stringes = [];
Should i do it with regular expressions? I think I need an help

You can just use str.split :
var stringa = "14:30 - 19:30";
var res = str.split("-");

If you know that the only '-' present will be the delimiter, you can start by splitting on that:
let parts = input.split('-');
If you need to get rid of whitespace surrounding that, you should trim each part:
parts = parts.map(function (it) { return it.trim(); });
To validate those parts, you can use a regex:
parts = parts.filter(function (it) { return /^\d\d:\d\d$/.test(it); });
Combined:
var input = "14:30 - 19:30";
var parts = input.split('-').map(function(it) {
return it.trim();
}).filter(function(it) {
return /^\d\d:\d\d$/.test(it);
});
document.getElementById('results').textContent = JSON.stringify(parts);
<pre id="results"></pre>

Try this :
var stringa = "14:30 - 19:30";
var stringes = stringa.split("-"); // string is "14:30-19:30" this style
or
var stringes = stringa.split(" - "); // if string is "14:30 - 19:30"; style so it includes the spaces also around '-' character.
The split function breaks the strings in sub-strings based on the location of the substring you enter inside it "-"
. the first one splits it based on location of "-" and second one includes the spaces also " - ".
*also it looks more like 24 hour clock time format than data as you mentioned in your question.

var stringa = '14:30 - 19:30';
var stringes = stringa.split("-");

.split is probably the best way to go, though you will want to prep the string first. I would go with str.replace(/\s*-\s*/g, '-').split('-'). to demonstrate:
var str = "14:30 - 19:30"
var str2 = "14:30-19:30"
console.log(str.replace(/\s*-\s*/g, '-').split('-')) //outputs ["14:30", "19:30"]
console.log(str2 .replace(/\s*-\s*/g, '-').split('-')) //outputs ["14:30", "19:30"]

Don't forget that you can pass a RegExp into str.split
'14:30 - 19:30'.split(/\s*-\s*/); // ["14:30", "19:30"]
'14:30-19:30'.split(/\s*-\s*/); // ["14:30", "19:30"]

Javascript Regex replace by group

Suppose you have this string: url?param1=something&param2=something&param3=something which can also be only url?param1=something.
How would you do to convert param1=something to param1=anotherthing ?
I am able to do it this way:
var regex = /param1=.*(&|$)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, 'param1='+newValue);
However, I do not like the fact of repeating all the search term, so I'm asking if it is possible to group the needed pattern to replace, in this case would be .* and replace only that.
For example, saying that $1 belongs to group 1. This is fictitious.
var regex = /param1=(.*)(&|$)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, $1, newValue);

Try this:
var string = 'url?param1=something&param2=something&param3=something';
alert(string.replace(/(param1)([^&]+)/, '$1=newparam1'));
if you want to set multiple parameters to the same value
alert(string.replace(/(param1|param2)([^&]+)/g, '$1=newparam'));

Add another capture group...
var regex = /(param1=)([^&]*)/;
var string = 'url?param1=something&param2=something&param3=something';
var newValue = 'anotherthing';
string.replace(regex, "$1" + newValue);

Search through string with Javascript

Say I have a string like this:
jJKld-xxx-JKl122
Using javascript, how can I get on what's in-between the - characters? In others words, all I need to do is put whatever is xxx into a variable.
Thanks

If the string is always in that format, this will work:
var foo = 'jJKld-xxx-JKl122';
var bar = foo.split('-')[1]; // = xxx

just try it with this simple regex
var str = 'jJKld-xxx-JKl122';
var xxx = str.replace( /^[^\-]*-|-[^\-]*$/g, '' );

You can simply use the following regex to get the result
var myString = "jJKld-xxx-JKl122";
var myRegexp = /(?:^|\s*)-(.*?)-(?:^|\s*)/g;
var match = myRegexp.exec(myString);
alert(match[1]);
See the demo here

get particular string part in javascript

I have a javascript string like "firstHalf_0_0_0" or secondHalf_0_0_0". Now I want to get the string before the string "Half" from above both strings using javascript.Please help me.
Thanks.

var myString = "firstHalf_0_0_0";
var parts = myString.split("Half");
var thePart = parts[0];

var str = 'firstHalf_0_0_0',
part = str.match(/(\w+)Half/)[1];
alert(part); // Alerts "first"

var str = "firstHalf.....";
var index = str.indexOf("Half");
var substring = str.substr(0, index);
jsFiddle demo.

Using this you can get any particular part of string.
var str= 'your string';
var result = str.split('_')[0];

Working example here for your particular case.
http://jsfiddle.net/7kypu/3/
cheers!

Quick Problem - Extracting numbers from a string

I need to extract a single variable number from a string. The string always looks like this:
javascript:change(5);
with the variable being 5.
How can I isolate it? Many thanks in advance.

Here is one way, assuming the number is always surrounded by parentheses:
var str = 'javascript:change(5);';
var lastBit = str.split('(')[1];
var num = lastBit.split(')')[0];

Use regular expressions:-
var test = "javascript:change(5);"
var number = new RegExp("\\d+", "g")
var match = test.match(number);
alert(match);

A simple RegExp can solve this one:
var inputString = 'javascript:change(5);';
var results = /javascript:change\((\d+)\)/.exec(inputString);
if (results)
{
alert(results[1]); // 5
}
Using the javascript:change part in the match as well ensures that if the string isn't in the proper format, you wont get a value from the matches.

var str = 'javascript:change(5);', result = str.match(/\((\d+)\)/);
if ( result ) {
alert( result[1] )
}