Develop Reference

replace number from the middle using javascript / node js

var str = "demo-test-1-0-4_testing.pdf";
I have a string i want to replace with word verified
so my expected value look like this
str= demo-test-verified_testing.pdf
I can do this if the numbers are written in last like this
var str = "demo-test-1-0-1";
str = str.replace(/(?!(-| |_))(\d|-|\.)+\s*$/, "verified");
console.log(str);
but in middle I don't know
as my expected value is like this demo-test-verified_testing.pdf as i want to replace 1-0-1 i can use replace function but every time version get updated so number get changed that's why i cant use replace function

This should be enough:
var str = "demo-test-1-0-4_testing.pdf";
str = str.replace(/(-\d+)+/,"-verified")
console.log(str)
str = "demo-test-1-0-1"
str = str.replace(/(-\d+)+/,"-verified")
console.log(str)
var str = "demo-test-1-0-41_testing.pdf";
str = str.replace(/(-\d+)+/,"-verified")
console.log(str)

reg expression created from variable not working in .replace()

I'm doing a coding challenge that wants us to create a function that finds and replaces a word in a sentence. I define the reg expression like this
//"before" is the parameter with the word to be replaced
var regRep = '/'+before+'/gi';
and I'm using it like this
//"str" is the sentence to search and prepAfter" is a variable with the replacement word.
var newStr = str.replace(regRep, prepAfter);
when returning newStr I get the original str without any modifications. I went through and console.log()ed each of my variables and chunks of logic and the replace() method is the only thing not working as it's suppose to. Here's the entire function.
function myReplace(str, before, after) {
var prepAfter = "";
var caseCheck = before.charAt(0);
var regRep = '/'+before+'/gi';
if(caseCheck === caseCheck.toUpperCase()){
var firstLetter = after.substr(0,1).toUpperCase();
var wordLength = after.length -1;
var remWord = after.substr(1,wordLength);
prepAfter = firstLetter.concat(remWord);
}
else{ prepAfter = after; }
var newStr = str.replace(regRep, prepAfter);
return newStr;
}
What am I missing?

var regRep = new RegExp(before, 'gi');
If you pass a string to replace() (as you did), it will look for the actual string.
Note: if before is just a word in your case, you might not even need a regex, just passing it to replace() as-is could do. Depends on whether or not you need to check things like whitespace before and after.

Extract words with RegEx

I am new with RegEx, but it would be very useful to use it for my project. What I want to do in Javascript is this :
I have this kind of string "/this/is/an/example" and I would like to extract each word of that string, that is to say :
"/this/is/an/example" -> this, is, an, example. And then use each word.
Up to now, I did :
var str = "/this/is/a/test";
var patt1 = /\/*/g;
var result = str.match(patt1);
document.getElementById("demo").innerHTML = result;
and it returns me : /,,,,,/,,,/,,/,,,,,
I know that I will have to use .slice function next if I can identify the position of each "/" by using search for instance but using search it only returns me the index of the first "/" that is to say in this case 0.
I cannot find out.
Any Idea ?
Thanks in advance !

Use split()
The split() method splits a String object into an array of strings by separating the string into substrings, using a specified separator string to determine where to make each split.
var str = "/this/is/a/test";
var array = str.split('/');
console.log(array);
In case you want to do with regex.
var str = "/this/is/a/test";
var patt1 = /(\w+)/g;
var result = str.match(patt1)
console.log(result);

Well I guess it depends on your definition of 'word', there is a 'word character' match which might be what you want:
var patt1 = /(\w+)/g;
Here is a working example of the regex
Full JS example:
var str = "/this/is/a/test";
var patt1 = /(\w+)/g;
var match = str.match(patt1);
var output = match.join(", ");
console.log(output);

You can use this regex: /\b[^\d\W]+\b/g, to have a specific word just access the index in the array. e.g result[0] == this
var str = "/this/is/a/test";
var patt1 = /\b[^\d\W]+\b/g;
var result = str.match(patt1);
document.getElementById("demo").innerHTML = result;
<span id="demo"></span>

How to use Javascript slice to extract first and last letter of a string?

How to use JavaScript slice to extract the first and last letter of a string?
Eg: "Hello World"
I need the result as "dH".
Following is my jsfiddle :
http://jsfiddle.net/vSAs8/

Here's the cleanest solution :
var output = input.slice(-1)+input[0];
If you want more slice, there's also
var output = input.slice(-1)+input.slice(0,1);
And here are alternate fun (and less efficient) solutions :
var output = input.replace(/^(.).*(.)$/,'$2$1');
or
var output = input.match(/^.|.$/g).reverse().join('');

Substr works as well:
alert(test.substr(-1,1) + test.substr(0,1));

a.charAt(a.length-1) + a.charAt(0)

var str = " Virat Kohali "
var get_string_label = function(str){
str = str.split(" ");
str = str.filter(res=>res.length>0);
str = str.map(function(res){
return res[0].toUpperCase();
});
str = str.join("");
return str;
};
console.log(get_string_label(str));
str.split(" "); method splits a String object into an array of strings by separating the string into substrings, where it will find space in string.
then str.filter(res=>res.length>0) will filter out string having zero length (for "virat kohali" string you will get empty sub-string)
after that using map function you can fetch your first letter

Regex remove repeated characters from a string by javascript

I have found a way to remove repeated characters from a string using regular expressions.
function RemoveDuplicates() {
var str = "aaabbbccc";
var filtered = str.replace(/[^\w\s]|(.)\1/gi, "");
alert(filtered);
}
Output: abc
this is working fine.
But if str = "aaabbbccccabbbbcccccc" then output is abcabc.
Is there any way to get only unique characters or remove all duplicates one?
Please let me know if there is any way.

A lookahead like "this, followed by something and this":
var str = "aaabbbccccabbbbcccccc";
console.log(str.replace(/(.)(?=.*\1)/g, "")); // "abc"
Note that this preserves the last occurrence of each character:
var str = "aabbccxccbbaa";
console.log(str.replace(/(.)(?=.*\1)/g, "")); // "xcba"
Without regexes, preserving order:
var str = "aabbccxccbbaa";
console.log(str.split("").filter(function(x, n, s) {
return s.indexOf(x) == n
}).join("")); // "abcx"

This is an old question, but in ES6 we can use Sets. The code looks like this:
var test = 'aaabbbcccaabbbcccaaaaaaaasa';
var result = Array.from(new Set(test)).join('');
console.log(result);