I am having a ridiculous time trying to simply remove a path from a pathname in Node JS. I think the problem is that replace is not working because the base string has slashes. But I can't seem to figure out any way to operate on the string properly. When I do replace sometimes it just removes the slashes entirely and doesn't even replace with what I asked it to.
Example.... where the heck did the slashes even go.
'C:\path\build\test\subfolder'.replace('b', 'z')
// "C:path\build\testsuzfolder"
Anyway what I'm actually trying to do is this.
Given this path I get.
C:\path\build\test\subfolder
Remove
C:\path\build\test\
But no amount of attempts with replace is working, even if I escape slashes.
Node was giving me __dirname with those slashes so there was no string function to do what I needed. So I had to use split with Node's special path.sep and then rejoin with the other slash type.
let formatted_folder = folder.split(path.sep).join('/');
According to your description of what you want, you should do
const path = require('path');
const idx = __dirname.lastIndexOf(path.sep);
const res = __dirname.slice(idx);
(or idx + 1, if you don't need the separator itself in the result).
I am trying to replace the filepath with just the filename using regex, and struggling.
I take a list of text like this:
xlink:href="file://C:\x\y & DRAWINGS\z - CONTROLLED\a \testsvg-A01.svg"
and i just want to output
xlink:href="testsvg-A01.svg"
I can get there with separate regex (javascript) with several bits of regex as such:
let inQuotes = hrefs[0].match(/"(.*?)"/gm);
inQuotes = inQuotes[0].match(/([^\\]+$)/gm);
inQuotes = inQuotes[0].replace(/"/g, "");
this will return just the filename, but i was wondering if there was a way to take this and replace the original text to the desired style.
EDIT:
i can get it for a single occurrance with this line of code:
let testHrefs = outText.match(/xlink:href="(.*?)"/gm)[0].match(/"(.*?)"/gm)[0].match(/([^\\]+$)/gm)[0].replace(/^/, 'xlink:href="');
but it looks awful and doesn't completely do what i want. Any advice?
You could use a regex to remove the text you don't want to keep (i.e. everything between the href=" and the filename:
let href = 'xlink:href="file://C:\\x\\y & DRAWINGS\\z - CONTROLLED\\a \\testsvg-A01.svg"';
console.log(href);
console.log(href.replace(/href=".*?([^\\\/]+)$/, 'href="$1'));
Note I've used [\\\/] to allow for Unix and Windows style filenames, if you only want Windows style filenames that can simply be [\\].
First, keep in mind that backslashes in strings need to be escaped, as the backslash itself is an escape character. You'll likely want to escape these as \\.
After doing this, you can make use of a positive look-behind on the \ with the regex (?<=\\)[^\\]*:
var xlink = "file://C:\\x\\y & DRAWINGS\\z - CONTROLLED\\a \\testsvg-A01.svg";
var regex = /(?<=\\)[^\\]*/gm;
console.log(xlink.match(regex));
This splits the string into each of the folders (which may be useful within itself), though if you exclusively want the filename, you can use xlink.match(regex)[4] (assuming the length is consistent), or xlink.match(regex)[xlink.match(regex).length - 1] if it isn't.
var xlink = "file://C:\\x\\y & DRAWINGS\\z - CONTROLLED\\a \\testsvg-A01.svg";
var regex = /(?<=\\)[^\\]*/gm;
console.log(xlink.match(regex)[xlink.match(regex).length - 1]);
Problem:
Extract image file name from CDN address similar to the following:
https://cdnstorage.api.com/v0/b/my-app.com/o/photo%2FB%_2.jpeg?alt=media&token=4e32-a1a2-c48e6c91a2ba
Two-stage Solution:
I am using two regular expressions to retrieve the file name:
var postLastSlashRegEx = /[^\/]+$/,
preQueryRegEx = /^([^?]+)/;
var fileFromURL = urlString.match(postLastSlashRegEx)[0].match(preQueryRegEx)[0];
// fileFromURL = "photo%2FB%_2.jpeg"
Question:
Is there a way I can combine both regular expressions?
I've tried using capture groups, but haven't been able to produce a working solution.
From my comment
You can use a lookahead to find the "?" and use [^/] to match any non-slash characters.
/[^/]+(?=\?)/
To remove the dependency on the URL needing a "?", you can make the lookahead match a question mark or the end of line indicator (represented by $), but make sure the first glob is non-greedy.
/[^/]+?(?=\?|$)/
You don't have to use regex, you can just use split and substr.
var str = "https://cdnstorage.api.com/v0/b/my-app.com/o/photo%2FB%_2.jpeg?alt=media&token=4e32-a1a2-c48e6c91a2ba".split("?")[0];
var fileName = temp.substr(temp.lastIndexOf('/')+1);
but if regex is important to you, then:
str.match(/[^?]*\/([^?]+)/)[1]
The code using the substring method would look like the following -
var fileFromURL = urlString.substring(urlString.lastIndexOf('/') + 1, urlString.lastIndexOf('?'))
What are the actual uses of String.raw Raw String Access introduced in ECMAScript 6?
// String.raw(callSite, ...substitutions)
function quux (strings, ...values) {
strings[0] === "foo\n"
strings[1] === "bar"
strings.raw[0] === "foo\\n"
strings.raw[1] === "bar"
values[0] === 42
}
quux `foo\n${ 42 }bar`
String.raw `foo\n${ 42 }bar` === "foo\\n42bar"
I went through the below docs.
http://es6-features.org/#RawStringAccess
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/template_strings
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/raw
http://www.2ality.com/2015/01/es6-strings.html
https://msdn.microsoft.com/en-us/library/dn889830(v=vs.94).aspx
The only the thing that I understand, is that it is used to get the raw string form of template strings and used for debugging the template string.
When this can be used in real time development? They were calling this a tag function. What does that mean?
What concrete use cases am I missing?
The best, and very nearly only, use case for String.raw I can think of is if you're trying to use something like Steven Levithan's XRegExp library that accepts text with significant backslashes. Using String.raw lets you write something semantically clear rather than having to think in terms of doubling your backslashes, just like you can in a regular expression literal in JavaScript itself.
For instance, suppose I'm doing maintenance on a site and I find this:
var isSingleUnicodeWord = /^\w+$/;
...which is meant to check if a string contains only "letters." Two problems: A) There are thousands of "word" characters across the realm of human language that \w doesn't recognize, because its definition is English-centric; and B) It includes _, which many (including the Unicode consortium) would argue is not a "letter."
So if we're using XRegExp on the site, since I know it supports \pL (\p for Unicode categories, and L for "letter"), I might quickly swap this in:
var isSingleUnicodeWord = XRegExp("^\pL+$"); // WRONG
Then I wonder why it didn't work, facepalm, and go back and escape that backslash, since it's being consumed by the string literal.
Easy enough in that simple regex, but in something complicated, remembering to double all those backslashes is a maintenance pain. (Just ask Java programmers trying to use Pattern.)
Enter String.raw:
let isSingleUnicodeWord = XRegExp(String.raw`^\pL+$`);
Example:
let isSingleUnicodeWord = XRegExp(String.raw`^\pL+$`); // L: Letter
console.log(isSingleUnicodeWord.test("Русский")); // true
console.log(isSingleUnicodeWord.test("日本語")); // true
console.log(isSingleUnicodeWord.test("العربية")); // true
console.log(isSingleUnicodeWord.test("foo bar")); // false
<script src="https://cdnjs.cloudflare.com/ajax/libs/xregexp/3.1.1/xregexp-all.min.js"></script>
Now I just kick back and write what I mean. I don't even really have to worry about ${...} constructs used in template literals to do substitution, because the odds of my wanting to apply a quantifier {...} to the end-of-line assertion ($) are...low. So I can happily use substitutions and still not worry about backslashes. Lovely.
Having said that, though, if I were doing it a lot, I'd probably want to write a function and use a tagged template instead of String.raw itself. But it's surprisingly awkward to do correctly:
// My one-time tag function
function xrex(strings, ...values) {
let raw = strings.raw;
let max = Math.max(raw.length, values.length);
let result = "";
for (let i = 0; i < max; ++i) {
if (i < raw.length) {
result += raw[i];
}
if (i < values.length) {
result += values[i];
}
}
console.log("Creating with:", result);
return XRegExp(result);
}
// Using it, with a couple of substitutions to prove to myself they work
let category = "L"; // L: Letter
let maybeEol = "$";
let isSingleUnicodeWord = xrex`^\p${category}+${maybeEol}`;
console.log(isSingleUnicodeWord.test("Русский")); // true
console.log(isSingleUnicodeWord.test("日本語")); // true
console.log(isSingleUnicodeWord.test("العربية")); // true
console.log(isSingleUnicodeWord.test("foo bar")); // false
<script src="https://cdnjs.cloudflare.com/ajax/libs/xregexp/3.1.1/xregexp-all.min.js"></script>
Maybe the hassle is worth it if you're using it in lots of places, but for a couple of quick ones, String.raw is the simpler option.
First, a few things:
Template strings is old name for template literals.
A tag is a function.
String.raw is a method.
String.raw `foo\n${ 42 }bar\` is a tagged template literal.
Template literals are basically fancy strings.
Template literals can interpolate.
Template literals can be multi-line without using \.
String.raw is required to escape the escape character \.
Try putting a string that contains a new-line character \n through a function that consumes newline character.
console.log("This\nis\nawesome"); // "This\nis\nawesome"
console.log(String.raw`This\nis\nawesome`); // "This\\nis\\nawesome"
If you are wondering, console.log is not one of them. But alert is. Try running these through http://learnharmony.org/ .
alert("This\nis\nawesome");
alert(String.raw`This\nis\nawesome`);
But wait, that's not the use of String.raw.
Possible uses of String.raw method:
To show string without interpretation of backslashed characters (\n, \t) etc.
To show code for the output. (As in example below)
To be used in regex without escaping \.
To print windows director/sub-directory locations without using \\ to much. (They use \ remember. Also, lol)
Here we can show output and code for it in single alert window:
alert("I printed This\nis\nawesome with " + Sring.raw`This\nis\nawesome`);
Though, it would have been great if It's main use could have been to get back the original string. Like:
var original = String.raw`This is awesome.`;
where original would have become: This\tis \tawesome.. This isn't the case sadly.
References:
http://exploringjs.com/es6/ch_template-literals.html
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/raw
Template strings can be useful in many situations which I will explain below. Considering this, the String.raw prevents escapes from being interpreted. This can be useful in any template string in which you want to contain the escape character but do not want to escape it. A simple example could be the following:
var templateWithBackslash = String.raw `someRegExp displayed in template /^\//`
There are a few things inside that are nice to note with template strings.
They can contain unescaped line breaks without problems.
They can contain "${}". Inside these curly braces the javascript is interpreted instead.
(Note: running these will output the result to your console [in browser dev tools])
Example using line breaks:
var myTemplate = `
<div class="myClass">
<pre>
My formatted text
with multiple lines
{
asdf: "and some pretty printed json"
}
</pre>
</div>
`
console.log(myTemplate)
If you wanted to do the above with a normal string in Javascript it would look like the following:
var myTemplate = "\
<div class="myClass">\
<pre>\
My formatted text\
with multiple lines\
{\
asdf: "and some pretty printed json"\
}\
</pre>\
</div>"
console.log(myTemplate)
You will notice the first probably looks much nicer (no need to escape line breaks).
For the second I will use the same template string but also insert the some pretty printed JSON.
var jsonObj = {asdf: "and some pretty printed json", deeper: {someDeep: "Some Deep Var"}}
var myTemplate = `
<div class="myClass">
<pre>
My formatted text
with multiple lines
${JSON.stringify(jsonObj, null, 2)}
</pre>
</div>
`
console.log(myTemplate)
In NodeJS it is extremely handy when it comes to filepath handling:
var fs=require('fs');
var s = String.raw`C:\Users\<username>\AppData\Roaming\SomeApp\someObject.json`;
var username = "bob"
s=s.replace("<username>",username)
fs.readFile(s,function(err,result){
if (err) throw error;
console.log(JSON.parse(result))
})
It improves readability of filepaths on Windows. \ is also a fairly common separator, so I can definitely see why it would be useful in general. However it is pretty stupid how \ still escapes `... So ultimately:
String.raw`C:\Users\` //#==> C:\Users\`
console.log(String.raw`C:\Users\`) //#==> SyntaxError: Unexpected end of input.
In addition to its use as a tag, String.raw is also useful in implementing new tag functions as a tool to do the interleaving that most people do with a weird loop. For example, compare:
function foo(strs, ...xs) {
let result = strs[0];
for (let i = 0; i < xs.length; ++i) {
result += useFoo(xs[i]) + strs[i + 1];
}
return result;
}
with
function foo(strs, ...xs) {
return String.raw({raw: strs}, ...xs.map(useFoo));
}
The Use
(Requisite knowledge: tstring §.)
Instead of:
console.log(`\\a\\b\\c\\n\\z\\x12\\xa9\\u1234\\u00A9\\u{1234}\\u{00A9}`);
.you can:
console.log(String.raw`\a\b\c\n\z\x12\xa9\u1234\u00A9\u{1234}\u{00A9}`);
"Escaping"
<\\u> is fine, yet <\u> needs "escaping", eg:
console.log(String.raw`abc${'\\u'}abc`);
.Dit <\\x>, <\x>,
<console.log(String.raw`abc${`\\x`}abc`)>;
.<\`>, <`>, <console.log(String.raw`abc${`\``}abc`)>;
.<\${>, <${&>, <console.log(String.raw`abc${`$\{`}abc`)>;
.<\\1> (till <\\7>), <\1>, <console.log(String.raw`abc${`\\1`}abc`)>;
.<\\>, endunit <\>, <console.log(String.raw`abc${`\\`}`)>.
Nb
There's also a new "latex" string. Cf §.
I've found it to be useful for testing
my RegExps. Say I have a RegExp which
should match end-of-line comments because
I want to remove them. BUT, it must not
match source-code for a regexp like /// .
If your code contains /// it is not the
start of an EOL comment but a RegExp, as
per the rules of JavaScript syntax.
I can test whether my RegExp in variable patEOLC
matches or doesn't /// with:
String.raw`/\//` .match (patEOLC)
In other words it is a way to let my
code "see" code the way it exists in
source-code, not the way it exists
in memory after it has been read
into memory from source-code, with
all backslashes removed.
It is a way to "escape escaping" but
without having to do it separately
for every backslash in a string, but
for all of them at the same time.
It is a way to say that in a given
(back-quoted) string backslash
shall behave just like any other
character, it has no special
meaning or interpretation.
I have this regular expression
// Look for /en/ or /en-US/ or /en_US/ on the URL
var matches = req.url.match( /^\/([a-zA-Z]{2,3}([-_][a-zA-Z]{2})?)(\/|$)/ );
Now with the above regular express it will cause the problem with the URL such as:
http://mydomain.com/css/bootstrap.css
or
http://mydomain.com/js/jquery.js
because my regular expression is to strip off 2-3 characters from A-Z or a-z
My question is how would I add in to this regular expression to not strip off anything with
js or img or css or ext
Without impacting the original one.
I'm not so expert on regular expression :(
Negative lookahead?
var matches = req.url.match(/^\/(?!(js|css))([a-zA-Z]{2,3}([-_][a-zA-Z]{2})?)(\/|$)/ );
\ not followed by js or css
First of all you have not defined what exactly you are searching for.
Define an array with lowercased common language codes (Common language codes)
This way you'll know what to look for.
After that, convert your url to lowercase and replace all '_' with '-' and search for every member of the array in the resulting string using indexOf().
Since you said you're using the regex to replace text, I changed it to a replace function. Also, you forced the regex to match the start of the string; I don't see how it would match anything with that. Anyway, here's my approach:
var result = req.url.replace(/\/([a-z]{2,3}([-_][a-z]{2})?)(?=\/|$)/i,
function(s,t){
switch(t){case"js":case"img":case"css":case"ext":return s;}
return "";
}
);