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When to Use Double or Single Quotes in JavaScript
Difference between single quotes and double quotes in Javascript
When I started learning jQuery, I frequently found examples using single quote or double quote as jQuery selector:
$('#myDiv'); or $("#myDiv");
They are basically the same. But which one is used prefer and fast execute please let me know.
You'll want to use single quotes where you want double quotes to appear inside the string (e.g. for html attributes) without having to escape them, or vice-versa. Other than that, there is no difference, performance vise also both are same.
There's no performance difference. They mean the same thing. I usually use singles for property names and other short literals, and doubles for long text that the user will see. The exception of course, is when one of the two appears inside the string, then use the other.
Personally I use double quotes when working with strings (= more than one char) and single quotes when working with chars (= one char) although there is no difference in Javascript. There's also no "hidden" feature in double quotes like there is in php.
jQuery code style mandates the use of double-quotes, but there's no diference in usage.
Double quotes are typed faster =)
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I've been trying to create a RegExp that makes sure a sure has entered at least one word and at least one space. I tried to use this:
/\w+\s+/
But that makes sure that there is a word AFTER a space. I just want to make sure there is both in a string. They don't need to be in the order of the above RegExp.
How can I make the RegExp work, but without matching the order?
/(?=.*?\w)(?=.*?\s)/
?= means "look-ahead", and .* means "any number of characters"
So "find any number of characters then a \w", "find any number of characters and a \s"
Another thing to note about how this works, look-aheads are "non-matching", making it so that this can match in any order.
You have two things:
Is there a word character?
Is there a space?
Two things.
str.match(/\w/)
str.match(/\s/)
So why are you trying to do them as one step?
if( str.match(/\w/) && str.match(/\s/))
There are a lot of answers to my question. However, I do not want to simply pick the one that is upvoted. Please give a detailed explanation of why your regex works, and maybe why mine doesn't.
My answer provides the simplest solution. It is very clear to anyone reading it that we are checking "if it has a word character, and if it contains a space character". It is also very easy to expand on, such as if you want to add another check.
zyklus' answer (/(?=.*?\w)(?=.*?\s)/) is the fastest when speed-tested on a 50Kb string of input. In more common cases (ie. 100 character at most), this speed difference will be practically non-existent. It is twice as fast as my answer, but "2 * very small number = very small number". It's easy enough to add new test cases (just add another (?=.*something) block) but is less humanly-obvious as to what it does.
Jacob's answer ((\w+.*\s+)|(\s+.*\w+)) does quite literally what you asked, checking first if there is a word character and then a space character, then checks the other way around before failing. It works, however it is slower. Furthermore, if you decide to add a new test case, you'd get something like (\w+.*\s+.*\d+)|(\w+.*\d+.*\s)|(\s+.*\w+.*\d+)|(\s+.*\d+.*\w+)|(\d+.*\w+.*\s+)|(\d+.*\s+.*\w+). It only gets worse if you add a fourth test (24 arrangements to check) and is unreadably ugly. Do not use this answer.
Other answers are variants of existing ones.
If you need to do it in one RegEx for some reason:
(\w+.*\s+)|(\s+.*\w+)
Can be handy if you're working with a library that only enables you to use a single regular expression.
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How do I trim a string in javascript?
Using JavaScript without any frameworks how would you trim line breaks? Trim as being defined by PHP, removing the leading and ending line breaks while preserving line breaks after the first non-white-space character and until though not beyond the last non-white-space character.
By default most people will want to know how to remove both leading/ending line breaks as well as white-space spaces too though some may want to retain the white-space spaces while trimming just the white-space line-breaks. It also generally helps to see two working examples and how they relate when they both work for people learning code, so I'm looking for trimming both white-space line-breaks and white-space spaces.
It'd be good also to see how to trim just the leading/ending line breaks while preserving white-space spaces (which may or may not be included in the main answer).
I think this works:
string.replace(/^\s+|\s+$/g,"");
trim in general can be defined as .replace(/^\s+|\s+$/g,''), but since you want only vertical whitespace you should use .replace(/^[\r\n]+|[\r\n]+$/g,'').
Anyone knows a technique or method to find the position of the natural text line breaks in a textarea using javascript? It's not about finding \n or <br/>'s.
It is not possible to do this directly, but the answer to this question uses a trick to find them where it adds characters one by one and checks for scrolling:
finding "line-breaks" in textarea that is word-wrapping ARABIC text
For the sake of simplicity & learning something new, please don't suggest using two separate replace functions. I know that's an option but I would rather also know how to do this (or if it's not possible).
'<test></test>'.replace(/<|>/g,'$&'.charCodeAt(0))
This is what I've got so far. This sample code is, as you can tell, for another piece of code to escape HTML entities while still using innerHTML (because I do intend to include a few HTML entities such as small images, so again please don't suggest textContent).
Since I'm trying to replace both < and >, the problem is converting each individual one to their respective character codes. Since regular expressions allow for this "OR" condition as well as backreferences to each one, I'm hoping there's a way to get the reference of each individual character as they're replaced. $& will return <><> (because they're replaced in that order), but I don't know how to get them as they're replaced and take their character codes for the HTML entities. The problem is, I don't know what to use in this case if anything.
If that explanation wasn't clear enough, I want it to be something like this (and this is obviously not going to work, it'll best convey what I mean):
Assuming x is the index of the character being replaced,
'<test></test>'.replace(/<|>/g,'$&'.charCodeAt(x))
Hopefully that makes more sense. So, is this actually possible in some way?
'<test></test>'.replace(/[<>]/g,function(a) {return '&#'+a.charCodeAt(0)+';';});
I've put the characters in a square-bracket-thing (don't know it's proper name). That way you can add whatever characters you want.
The above will return:
<test></test>
I am in the need of defining html classes from content, so pretty much every char could be used. According to html reference I may use cdata, so I should not run into problems. I figure though, that css and/or javascript/jquery won't play nicely with that.
Anyone has experience with what chars can be used without problems or if there is a function/plugin/.. that tidies the class names, so that they are usable?
css classnames must be the usual identifiers (http://www.w3.org/TR/CSS21/syndata.html#characters)
In CSS 2.1, identifiers (including
element names, classes, and IDs in
selectors) can contain only the
characters [A-Za-z0-9] and ISO 10646
characters U+00A1 and higher, plus the
hyphen (-) and the underscore (_);
they cannot start with a digit.
Javascript doesn't mind, since you will use classnames as Strings. So you can use any character as far as javascript is concerned.
If you want to strip your classnames down to the usable css subset, a simple regexp should be enough. If you want to encode your classnames into the same subset, it will be a little tougher, but I suppose you can try to Base64-encode them. Here are some jQuery plugins for base64 encoding/decoding.
As far as the class attribute is concerned you will run into problems using chars other than [a-z], [A-Z] and [_-].
For arbitrary data I would recommend the (upcoming with HTML5) data-x attribute.
See http://ejohn.org/blog/html-5-data-attributes/ for an example.
Cheers