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How to alternate the case of a string

I'm working on alternating the case of a string (for example asdfghjkl to AsDfGhJkL).
I tried to do this. I found some code that is supposed to do it, but it doesn't seem to be working.
var str="";
var txt=document.getElementById('input').value;
for (var i=0; i<txt.length; i+2){
str = str.concat(String.fromCharCode(txt.charCodeAt(i).toUpperCase()));
}

Here's a quick function to do it. It makes the entire string lowercase and then iterates through the string with a step of 2 to make every other character uppercase.
var alternateCase = function (s) {
var chars = s.toLowerCase().split("");
for (var i = 0; i < chars.length; i += 2) {
chars[i] = chars[i].toUpperCase();
}
return chars.join("");
};
var txt = "hello world";
console.log(alternateCase(txt));
HeLlO WoRlD
The reason it converts the string to an array is to make the individual characters easier to manipulate (i.e. no need for String.prototype.concat()).

Here an ES6 approach:
function swapCase(text) {
return text.split('').map((c,i) =>
i % 2 == 0 ? c.toLowerCase() : c.toUpperCase()
).join('');
}
console.log(swapCase("test"))

You should iterate the string and alternate between upper-casing the character and lower-casing it:
for (var i=0; i<txt.length; i++) {
var ch = String.fromCharCode(txt.charCodeAt(i);
if (i % 2 == 1) {
ch = ch.toUpperCase();
} else {
ch = ch.toLowerCase();
}
str = str.concat(ch);
}

Decoding string to array values in javascript

I have 2 strings with some chars. One of them is with "mashed" characters, and the other one is with ordered characters which have some sense. For example:
wvEr2JmJUs2JRr:7Fob9WIB8mSOA?w0s2E:7-f/-G/N-.f7jN:Mi:.CDfGX7tn!
Identification: zpE?bkHlfYS-hIDate: 07/08/2057 12:34:56.789 CGT
So as you may see - the first one have equivalent of symbols which are the same for the equal symbol in the second one.
And the task is - to create somehow kind of alphabet from them, because I have third one string wich have to be "decoded". (wvEr2JmJUs2JRr:7a1AJvvHvAmRRWsxWsFAvJvAJAaoE88A2?s2AxJ1?290s2E:7-f/-G/N-.f7jN:MC:ifDCGN7tn!).
And the tricky part here is - that if I'm pretty sure for the first two strings that they're absolutely equal like a number of chars, so about the new one - is completely different number of symbols, but they consisting in the "alphabet"
And here is my current code for creation of the "alphabet":
var enc = "wvEr2JmJUs2JRr:7Fob9WIB8mSOA?w0s2E:7-f/-G/N-.f7jN:Mi:.CDfGX7tn!";
var dec = "Identification: zpE?bkHlfYS-hIDate: 07/08/2057 12:34:56.789 CGT";
var newenc = "wvEr2JmJUs2JRr:7a1AJvvHvAmRRWsxWsFAvJvAJAaoE88A2?s2AxJ1?290s2E:7-f/-G/N-.f7jN:MC:ifDCGN7tn!";
var myenc = {};
var mynewenc = {};
for (i = 0; i < enc.length; i+=1) {
var encoded = new Array(enc[i]);
var decoded = new Array(dec[i]);
myenc[enc[i]] = dec[i];
};
console.log(myenc);
And now - how I have to decode, the new one string, using this "alphabet"?

var enc = "wvEr2JmJUs2JRr:7Fob9WIB8mSOA?w0s2E:7-f/-G/N-.f7jN:Mi:.CDfGX7tn!";
var dec = "Identification: zpE?bkHlfYS-hIDate: 07/08/2057 12:34:56.789 CGT";
var newenc = "wvEr2JmJUs2JRr:7a1AJvvHvAmRRWsxWsFAvJvAJAaoE88A2?s2AxJ1?290s2E:7-f/-G/N-.f7jN:MC:ifDCGN7tn!";
function make_dictionary(enc, dec){
o = new Object();
if(enc.length == dec.length){
for(i=0; i<enc.length; i++){
o[enc[i]] = dec[i];
}
}
else{
console.log('error');
}
return o;
}
function translate(newenc, dictionary, fill){
var newstring = '';
for(i=0; i<newenc.length; i++){
if(typeof dictionary[newenc[i]] !== 'undefined'){
newstring += dictionary[newenc[i]];
}
else{
newstring += fill;
}
}
return newstring;
}
var d = make_dictionary(enc, dec);
console.log(d);
var string = translate(enc, d, '_');
console.log(string);
var string = translate(newenc, d, '_');
console.log(string);

Here's one way that you can approach it (as I understand the question):
// Create your dictionary
var dict = {};
var enc = "wvEr2JmJUs2JRr:7Fob9WIB8mSOA?w0s2E:7-f/-G/N-.f7jN:Mi:.CDfGX7tn!".split('');
var dec = "Identification: zpE?bkHlfYS-hIDate: 07/08/2057 12:34:56.789 CGT".split('');
// Populate your dictionary
for (var i = 0; i < enc.length; i++) {
dict[enc[i]] = dec[i];
}
// You can use your dictionary like this
var newenc = "wvEr2JmJUs2JRr:7a1AJvvHvAmRRWsxWsFAvJvAJAaoE88A2?s2AxJ1?290s2E:7-f/-G/N-.f7jN:MC:ifDCGN7tn!".split('');
// Returns your translated string
newenc.map(function(e) {
return dict[e];
}).join('');
However for this method you'll have to deal with characters that are defined in newenc that are not defined in your enc (such as T). I tried to do the best I could given the situation and rules that you've described, hope this helps!

If I understand well, you can try using this code.
It is finding the appropriate encoded letter in your enc variable and if the letter is found, it is replacing it with the corresponding letter from your dec variable.
var enc = "wvEr2JmJUs2JRr:7Fob9WIB8mSOA?w0s2E:7-f/-G/N-.f7jN:Mi:.CDfGX7tn!";
var dec = "Identification: zpE?bkHlfYS-hIDate: 07/08/2057 12:34:56.789 CGT";
var newenc = "wvEr2JmJUs2JRr:7a1AJvvHvAmRRWsxWsFAvJvAJAaoE88A2?s2AxJ1?290s2E:7-f/-G/N-.f7jN:MC:ifDCGN7tn!";
for (i = 0; i < newenc.length; i++) {
for (j = 0; j < enc.length; j++) {
if (enc[j] == newenc[i])
newenc[i] = dec[j];
}
};
console.log(newenc);
At the end your variable newenc may contain your decoded string.

Base 16 encoding of Uint8Array.buffer data

I am using javascript Uint8Array object.
I get a binary data out of it using '.buffer' property.
Due to some reasons I want to encode the binary data to base16 but I haven't got the clue yet.
Any help in the regard would be helpful.

Not sure if this is what you need
var b16 = "";
var u8 = [8,9,10,11]; // sample input
for(var x = 0; x < u8.length; x++) {
b16 += pad2(u8[x].toString(16));
}
function pad2(str) {
return (str.length < 2) ? "0"+str : str;
}
console.log(b16); // will return string "08090a0b"

var a = new Uint8Array(4);
function pad(str ) {
return str.length < 2 ? "0" + str : str;
}
[].map.call( a, function(v) {
return pad(v.toString(16));
}).join(""); //00000000

Random alpha-numeric string in JavaScript?

What's the shortest way (within reason) to generate a random alpha-numeric (uppercase, lowercase, and numbers) string in JavaScript to use as a probably-unique identifier?

I just came across this as a really nice and elegant solution:
Math.random().toString(36).slice(2)
Notes on this implementation:
This will produce a string anywhere between zero and 12 characters long, usually 11 characters, due to the fact that floating point stringification removes trailing zeros.
It won't generate capital letters, only lower-case and numbers.
Because the randomness comes from Math.random(), the output may be predictable and therefore not necessarily unique.
Even assuming an ideal implementation, the output has at most 52 bits of entropy, which means you can expect a duplicate after around 70M strings generated.

If you only want to allow specific characters, you could also do it like this:
function randomString(length, chars) {
var result = '';
for (var i = length; i > 0; --i) result += chars[Math.floor(Math.random() * chars.length)];
return result;
}
var rString = randomString(32, '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ');
Here's a jsfiddle to demonstrate: http://jsfiddle.net/wSQBx/
Another way to do it could be to use a special string that tells the function what types of characters to use. You could do that like this:
function randomString(length, chars) {
var mask = '';
if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
if (chars.indexOf('#') > -1) mask += '0123456789';
if (chars.indexOf('!') > -1) mask += '~`!##$%^&*()_+-={}[]:";\'<>?,./|\\';
var result = '';
for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() * mask.length)];
return result;
}
console.log(randomString(16, 'aA'));
console.log(randomString(32, '#aA'));
console.log(randomString(64, '#A!'));
Fiddle: http://jsfiddle.net/wSQBx/2/
Alternatively, to use the base36 method as described below you could do something like this:
function randomString(length) {
return Math.round((Math.pow(36, length + 1) - Math.random() * Math.pow(36, length))).toString(36).slice(1);
}

UPDATED:
One-liner solution, for random 20 characters (alphanumeric lowercase):
Array.from(Array(20), () => Math.floor(Math.random() * 36).toString(36)).join('');
Or shorter with lodash:
_.times(20, () => _.random(35).toString(36)).join('');

Another variation of answer suggested by JAR.JAR.beans
(Math.random()*1e32).toString(36)
By changing multiplicator 1e32 you can change length of random string.

Or to build upon what Jar Jar suggested, this is what I used on a recent project (to overcome length restrictions):
var randomString = function (len, bits)
{
bits = bits || 36;
var outStr = "", newStr;
while (outStr.length < len)
{
newStr = Math.random().toString(bits).slice(2);
outStr += newStr.slice(0, Math.min(newStr.length, (len - outStr.length)));
}
return outStr.toUpperCase();
};
Use:
randomString(12, 16); // 12 hexadecimal characters
randomString(200); // 200 alphanumeric characters

This is cleaner
Math.random().toString(36).substr(2, length)
Example
Math.random().toString(36).substr(2, 5)

function randomString(len) {
var p = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
return [...Array(len)].reduce(a=>a+p[~~(Math.random()*p.length)],'');
}
Summary:
Create an array of the size we want (because there's no range(len) equivalent in javascript.
For each element in the array: pick a random character from p and add it to a string
Return the generated string.
Some explanation:
[...Array(len)]
Array(len) or new Array(len) creates an array with undefined pointer(s). One-liners are going to be harder to pull off. The Spread syntax conveniently defines the pointers (now they point to undefined objects!).
.reduce(
Reduce the array to, in this case, a single string. The reduce functionality is common in most languages and worth learning.
a=>a+...
We're using an arrow function.
a is the accumulator. In this case it's the end-result string we're going to return when we're done (you know it's a string because the second argument to the reduce function, the initialValue is an empty string: ''). So basically: convert each element in the array with p[~~(Math.random()*p.length)], append the result to the a string and give me a when you're done.
p[...]
p is the string of characters we're selecting from. You can access chars in a string like an index (E.g., "abcdefg"[3] gives us "d")
~~(Math.random()*p.length)
Math.random() returns a floating point between [0, 1) Math.floor(Math.random()*max) is the de facto standard for getting a random integer in javascript. ~ is the bitwise NOT operator in javascript.
~~ is a shorter, arguably sometimes faster, and definitely funner way to say Math.floor( Here's some info

I think the following is the simplest solution which allows for a given length:
Array(myLength).fill(0).map(x => Math.random().toString(36).charAt(2)).join('')
It depends on the arrow function syntax.

for 32 characters:
for(var c = ''; c.length < 32;) c += Math.random().toString(36).substr(2, 1)

Random character:
String.fromCharCode(i); //where is an int
Random int:
Math.floor(Math.random()*100);
Put it all together:
function randomNum(hi){
return Math.floor(Math.random()*hi);
}
function randomChar(){
return String.fromCharCode(randomNum(100));
}
function randomString(length){
var str = "";
for(var i = 0; i < length; ++i){
str += randomChar();
}
return str;
}
var RandomString = randomString(32); //32 length string
Fiddle: http://jsfiddle.net/maniator/QZ9J2/

Using lodash:
function createRandomString(length) {
var chars = "abcdefghijklmnopqrstufwxyzABCDEFGHIJKLMNOPQRSTUFWXYZ1234567890"
var pwd = _.sampleSize(chars, length || 12) // lodash v4: use _.sampleSize
return pwd.join("")
}
document.write(createRandomString(8))
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

Random Key Generator
keyLength argument is the character length you want for the key
function keyGen(keyLength) {
var i, key = "", characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var charactersLength = characters.length;
for (i = 0; i < keyLength; i++) {
key += characters.substr(Math.floor((Math.random() * charactersLength) + 1), 1);
}
return key;
}
keyGen(12)
"QEt9mYBiTpYD"

var randomString = function(length) {
var str = '';
var chars ='0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz'.split(
'');
var charsLen = chars.length;
if (!length) {
length = ~~(Math.random() * charsLen);
}
for (var i = 0; i < length; i++) {
str += chars[~~(Math.random() * charsLen)];
}
return str;
};

When I saw this question I thought of when I had to generate UUIDs. I can't take credit for the code, as I am sure I found it here on stackoverflow. If you dont want the dashes in your string then take out the dashes. Here is the function:
function generateUUID() {
var d = new Date().getTime();
var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g,function(c) {
var r = (d + Math.random()*16)%16 | 0;
d = Math.floor(d/16);
return (c=='x' ? r : (r&0x7|0x8)).toString(16);
});
return uuid.toUpperCase();
}
Fiddle: http://jsfiddle.net/nlviands/fNPvf/11227/

This function should give a random string in any length.
function randString(length) {
var l = length > 25 ? 25 : length;
var str = Math.random().toString(36).substr(2, l);
if(str.length >= length){
return str;
}
return str.concat(this.randString(length - str.length));
}
I've tested it with the following test that succeeded.
function test(){
for(var x = 0; x < 300000; x++){
if(randString(x).length != x){
throw new Error('invalid result for len ' + x);
}
}
}
The reason i have chosen 25 is since that in practice the length of the string returned from Math.random().toString(36).substr(2, 25) has length 25. This number can be changed as you wish.
This function is recursive and hence calling the function with very large values can result with Maximum call stack size exceeded. From my testing i was able to get string in the length of 300,000 characters.
This function can be converted to a tail recursion by sending the string to the function as a second parameter. I'm not sure if JS uses Tail call optimization

A simple function that takes the length
getRandomToken(len: number): string {
return Math.random().toString(36).substr(2, len);
}
Ff you pass 6 it will generate 6 digit alphanumeric number

Nice and simple, and not limited to a certain number of characters:
let len = 20, str = "";
while(str.length < len) str += Math.random().toString(36).substr(2);
str = str.substr(0, len);

One could just use lodash uniqueId:
_.uniqueId([prefix=''])
Generates a unique ID. If prefix is given, the ID is appended to it.

Here's a simple code to generate random string alphabet.
Have a look how this code works.
go(lenthOfStringToPrint); - Use this function to generate the final string.
var letters = {
1: ["q","w","e","r","t","y","u","i","o","p","a","s","d","f","g","h","j","k","l","z","x","c","v","b","n","m"],
2: ["Q","W","E","R","T","Y","U","I","O","P","A","S","D","F","G","H","J","K","L","Z","X","C","V","B","N","M"]
},i,letter,final="";
random = (max,min) => {
return Math.floor(Math.random()*(max-min+1)+min);
}
function go(length) {
final="",letter="";
for (i=1; i<=length; i++){
letter = letters[random(0,3)][random(0,25)];
final+=letter;
}
return final;
}

I used #Nimphious excellent second approach and found that occasionally the string returned was numeric - not alphanumeric.
The solution I used was to test using !isNaN and use recursion to call the function again.
Why bother? I was using this function to create object keys, if all the keys are alphanumeric everything sorts properly but if you use
numbers as keys mixed with alphanumeric (strings) looping through the object will produce a different order to original order.
function newRandomString(length, chars) {
var mask = '';
if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
if (chars.indexOf('#') > -1) mask += '0123456789';
if (chars.indexOf('$') > -1) mask += '0123456789';
var result = '';
for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() *
mask.length)];
/*
we need a string not a number !isNaN(result)) will return true if '1234' or '3E77'
because if we're looping through object keys (created by newRandomString()) and
a number is used and all the other keys are strings then the number will
be first even if it was the 2nd or third key in object
*/
//use recursion to try again
if(!isNaN(result)){
console.log('found a number....:'+result);
return newRandomString(length, chars)
}else{
return result;
}
};
var i=0;
while (i < 1000) {
var a = newRandomString(4, '#$aA');
console.log(i+' - '+a);
//now we're using recursion this won't occur
if(!isNaN(a)){
console.log('=============='+i+' - '+a);
}
i++;
}
console.log('3E77:'+!isNaN('3E77'));//true
console.log('1234:'+!isNaN('1234'));//true
console.log('ab34:'+!isNaN('ab34'));//false

After looking at solutions in answers to this question and other sources, this is the solution that is simplest while allowing for modification of the included characters and selection in the length of the returned result.
// generate random string of n characters
function randomString(length) {
const characters = '0123456789abcdefghijklmnopqrstuvwxyz'; // characters used in string
let result = ''; // initialize the result variable passed out of the function
for (let i = length; i > 0; i--) {
result += characters[Math.floor(Math.random() * characters.length)];
}
return result;
}
console.log(randomString(6));

Use md5 library: https://github.com/blueimp/JavaScript-MD5
The shortest way:
md5(Math.random())
If you want to limit the size to 5:
md5(Math.random()).substr(0, 5)

How to convert from Hex to ASCII in JavaScript?

How to convert from Hex string to ASCII string in JavaScript?
Ex:
32343630 it will be 2460

function hex2a(hexx) {
var hex = hexx.toString();//force conversion
var str = '';
for (var i = 0; i < hex.length; i += 2)
str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
return str;
}
hex2a('32343630'); // returns '2460'

Another way to do it (if you use Node.js):
var input = '32343630';
const output = Buffer.from(input, 'hex');
log(input + " -> " + output); // Result: 32343630 -> 2460

For completeness sake the reverse function:
function a2hex(str) {
var arr = [];
for (var i = 0, l = str.length; i < l; i ++) {
var hex = Number(str.charCodeAt(i)).toString(16);
arr.push(hex);
}
return arr.join('');
}
a2hex('2460'); //returns 32343630

You can use this..
var asciiVal = "32343630".match(/.{1,2}/g).map(function(v){
return String.fromCharCode(parseInt(v, 16));
}).join('');
document.write(asciiVal);

** for Hexa to String**
let input = '32343630';
Note : let output = new Buffer(input, 'hex'); // this is deprecated
let buf = Buffer.from(input, "hex");
let data = buf.toString("utf8");

I found a useful function present in web3 library.
var hexString = "0x1231ac"
string strValue = web3.toAscii(hexString)
Update: Newer version of web3 has this function in utils
The functions now resides in utils:
var hexString = "0x1231ac"
string strValue = web3.utils.hexToAscii(hexString)

I've found that the above solution will not work if you have to deal with control characters like 02 (STX) or 03 (ETX), anything under 10 will be read as a single digit and throw off everything after. I ran into this problem trying to parse through serial communications. So, I first took the hex string received and put it in a buffer object then converted the hex string into an array of the strings like so:
buf = Buffer.from(data, 'hex');
l = Buffer.byteLength(buf,'hex');
for (i=0; i<l; i++){
char = buf.toString('hex', i, i+1);
msgArray.push(char);
}
Then .join it
message = msgArray.join('');
then I created a hexToAscii function just like in #Delan Azabani's answer above...
function hexToAscii(str){
hexString = str;
strOut = '';
for (x = 0; x < hexString.length; x += 2) {
strOut += String.fromCharCode(parseInt(hexString.substr(x, 2), 16));
}
return strOut;
}
then called the hexToAscii function on 'message'
message = hexToAscii(message);
This approach also allowed me to iterate through the array and slice into the different parts of the transmission using the control characters so I could then deal with only the part of the data I wanted.
Hope this helps someone else!

console.log(
"68656c6c6f20776f726c6421".match(/.{1,2}/g).reduce((acc,char)=>acc+String.fromCharCode(parseInt(char, 16)),"")
)

An optimized version of the implementation of the reverse function proposed by #michieljoris (according to the comments of #Beterraba and #Mala):
function a2hex(str) {
var hex = '';
for (var i = 0, l = str.length; i < l; i++) {
var hexx = Number(str.charCodeAt(i)).toString(16);
hex += (hexx.length > 1 && hexx || '0' + hexx);
}
return hex;
}
alert(a2hex('2460')); // display 32343630

I use this one, it seems more clear to me as I also receive data with spaces like '30 31 38 30 38 30' and the output is 018080
hexToString(hex: string): string {
return hex.split(' ').map(s => string.fromCharCode(parseInt(s,16))).join('');
}