Merge strings in javascript - javascript

I want to merge two variable with stings alternately using javascript. What would be an algorithm to accomplish this task?
For example:
var a = "abc"
var b = "def"
result = "adbecf"


I would use Array.from to generate an array from the strings (unicode conscious).
After that, just add a letter from each string until there's no letters left in each. Please note this solution will combine strings of uneven length (aa+bbbb=ababbb)
var a = "abc"
var b = "def"
var d = "foo 𝌆 bar mañana mañana"
function combineStrings(a,b){
var c = "";
a = Array.from(a);
b = Array.from(b);
while(a.length > 0 || b.length > 0){
if(a.length > 0)
c += a.splice(0,1);
if(b.length > 0)
c += b.splice(0,1);
}
return c;
}
var test = combineStrings(a,b);
console.log(test);
var test2 = combineStrings(a,d);
console.log(test2);


The best way to do this is to perform the following algorithm:
Iterate through string 1
For each character, if there is a character in the same position in string 2, replace the original character with both
This can be achieved with the following code:
function merge(s, t) {
return s.split("")
.map(function(v,i) {
return t[i] ? v + t[i] : v
})
.join("")
}
or the more Codegolf type answer:
s=>t=>[...s].map((v,i)=>t[i]?v+t[i]:v).join``


The simple way would be define the longest string and assigned to for loop. Also you have to add if statments for strings of uneven length, because you want to ignore undefined values of shorter string.
function mergeStrings(s1, s2){
var n = s1.length;
if(s1.length < s2.length){
n = s2.length;
}
var string = '';
for(var i = 0; i < n; i++){
if(s1[i]){
string += s1[i];
}
if(s2[i]){
string += s2[i];
}
}
return string;
}
console.log(mergeStrings('ab','lmnap'));
console.log(mergeStrings('abc','def'));


If your strings are the same length, this will work. If not you'll have to append the rest of the longer string after the loop. You can declare i outside of the loop and then use substr() to get the end of the longer string.
const a = "abc"
const b = "def"
var res = "";
for (var i = 0;i < Math.min(a.length, b.length); i++) {
res += a.charAt(i) + b.charAt(i)
}
console.log(res)


Regex or array processing and joining do the job:
let a = 'abc';
let b = 'def';
console.log(a.replace(/./g, (c, i) => c + b[i])); // 'adbecf'
console.log(Array.from(a, (c, i) => c + b[i]).join('')); // 'adbecf'


You can solve this using array spread and reduce. Split each string into an array and merge into one array and then use reduce to generate the merged string.
function mergeStrings(a, b) {
const mergedValues = [
...a.split(''),
...b.split('')
].reduce((values, currentValue) => {
if (!values.includes(currentValue)) {
values.push(currentValue);
}
return values;
}, []);
return Array.from(mergedValues).join('');
}

Related

How to flip every character with the character next to it. Javascript

Need help inside the for loop to flip each character with the character before it.
function flip(str) {
//split string
//iterate through split string
//return joined string
var splitt = str.split('');
for(var i = 0; i < splitt.length; i++){
//flip every character with one before it
}
}
var output = flip('otatl');
console.log(output); // -> 'total'

function split(str) {
let splitt = str.split('');
for (let i=0; i<splitt.length-1; i+=2) {
const temp = splitt[i];
splitt[i] = splitt[i+1];
splitt[i+1] = temp;
}
return splitt.join('');
}

You can use ES6 destructuring assignment.
function flip(str) {
//split string
//iterate through split string
//return joined string
let splitt = str.split('');
for (let i=0; i < splitt.length; i++){
//flip every character with one before it
if (i%2 == 1) {
[splitt[i-1], splitt[i]] = [splitt[i], splitt[i-1]];
}
}
return splitt.join('');
}
let output = flip('otatl');
console.log(output); // -> 'total'
You can combine this technique with gillyb's loop pattern to reduce the iterations as follows:
function flip(str) {
//split string
//iterate through split string
//return joined string
let splitt = str.split('');
for (let i=1; i < splitt.length; i+=2){
//flip every character with one before it
[splitt[i-1], splitt[i]] = [splitt[i], splitt[i-1]];
}
return splitt.join('');
}
let output = flip('otatl');
console.log(output); // -> 'total'

Can do something similar with regex and array manipulation
const flip = (stringToFlip) => stringToFlip
.split(/(.{2})/) // array of strings of 2 chars
.map((e) => e.split('') // convert each string piece to array
.reverse() // reverse array
.join('') // convert array piece back to string
)
.join(''); // combine all parts
const result = flip('otatl');
console.log("flip('otatl')");
console.log(result);

If we're not restricted to for loops, this is my (slightly too code golf-ish?) answer:
const flip = (str) =>
str
.split('')
.reduce((a, v, i) => (a[i + ((i % 2) * -2 + 1)] = v, a), [])
.join('');
console.log(flip('otatl'));
console.log(flip('lfpi'));

I'm sorry I am late to the party but you can use reduce().
let input = "vanjskojfdghpja";
let output = input
.split('')
.reduce(([o,p],c,i) => i%2?[o+c+p,'']:[o,c],['',''])
.join('');
console.log(output);
.as-console-wrapper { top: 0; max-height: 100% !important; }

Why is this returning an empty string?

I would like this to return s1 and s1 combined together, only the unique characters sorted in a new string called sortedString. Instead I get an empty string output.
ex input and output:
a = "xyaabbbccccdefww"
b = "xxxxyyyyabklmopq"
longest(a, b) -> "abcdefklmopqwxy"
function longest(s1, s2) {
var sortedString = '';
var a = s1.split();
var b = s2.split();
for (i=0; i < a.length; i++) {
if (!sortedString.includes(a[i])) {
sortedString.concat(a[i]);
}
}
for (j=0; j < b.length; j++) {
if (!sortedString.includes(b[j])) {
sortedString.concat(b[j]);
}
}
return sortedString.sort();
}

In javascript String type is immutable and concat method don't mutate input so when you type:
sortedString.concat(b[j]);
sortedString is never muted. You should make this instead :
sortedString = sortedString.concat(b[j]);

You need to pass an empty string to split if you want to separate the string into a list of characters.
However, I would strongly recommend you solve this declaratively:
const allChars = s1.split('').concat(s2.split(''));
return allChars
.filter((char) => allChars.indexOf(char) === allChars.lastIndexOf(char))
.sort()
.join('');

var a = "xyaabbbccccdefww";
var b = "xxxxyyyyabklmopq";
var mySet = new Set(a.split("").concat(b.split("")));
var result = Array.from(mySet).sort().join("");
console.log(result);

With ES6, you could use Set with spread syntax ... for splitting the string and for populating an array.
var a = "xyaabbbccccdefww",
b = "xxxxyyyyabklmopq",
result = [...new Set([...(a + b)])].sort().join("");
console.log(result);

how to cut a string in javascript

I'm receiving a String like this:
"45,21,555,64,94,796,488,\n " the \n means new line
is there a way to cut the string based on "," and getting only the "number".
I could do it C but how can I search for a character in JavaScript.
thanks for any hint

var parts = "45,21,555,64,94,796,488,\n ".split(',').filter(function(val) {
var num = parseInt(val, 10);
return !isNaN(num) && toString.call(num) === '[object Number]';
});
// parts: ["45", "21", "555", "64", "94", "796", "488"]
This is taking your String and splitting it into an Array based on a delimiter (',') and then running it through a filter function to remove anything that does not evaluate to a valid Number.
See String.prototype.split and Array.prototype.filter.
If you actually want to then convert those values to Numbers, you could chain a map call:
var parts = "45,21,555,64,94,796,488,\n ".split(',')
.filter(function(val) {
var num = parseInt(val, 10);
return !isNaN(num) && toString.call(num) === '[object Number]';
})
.map(function(val) {
return parseInt(val, 10);
});
// parts: [45, 21, 555, 64, 94, 796, 488]

Yes, like this:
var myString = "45,21,555,64,94,796,488,\n ";
var splitStrings = string.split(",");
console.log(splitStrings); //Should log an array to the console, containing only your strings e.g. [45,21,555,64,94,796,488,\n]
This returns an array of strings, split by the character you passed in. You can read more on this method here: http://www.w3schools.com/jsref/jsref_split.asp
After that, you can parse your array to remove anything you don't want like the new line character, or use a filter method to do it inline as detailed in another answer

You can use string.split(splitChar) to split. Then you can use .map or .filter to convert items to number.
var str = "45,21,555,64,94,796,488,\n ";
var arr = str.split(",");
document.write("Array: <pre>"+JSON.stringify(arr)+"</pre>");
var nums = arr.map(function(item){
return parseInt(item);
});
document.write("Numbers: <pre>"+JSON.stringify(nums)+"</pre>");

If you are wanting just the numbers as an array you could do this.
var str = "45,21,555,64,94,796,488,\n ";
var arr = str.split(","); //Make the string into an array
var len = arr.length;
for(var i=0;i<len;i++)
{
try
{
arr[i] = parseInt(arr[i]); // convert the numbers to ints
}
catch(e)
{
arr[i] = null;
}
}

As the fact that strings are just arrays, you can do it this way (a bit more comprehensive, in my opinion):
function noCommas(a)
{
var b = '';
for (var i = 0; i < a.length; i++)
{
if (a[i] != ',') //&& a[i]!= String.fromCharCode(10)) If you want no new lines too
{
b += a[i];
} else
{
//break; -> In case you only want the first value
}
}
return parseInt(b); //To return the value as an integer
}
noCommas('1234,6789'); // returns 12346789
I missunderstood the question, so here's my fixed code:
function noCommas(a)
{
var b = [];
var tempNum = '';
for (var i = 0; i < a.length; i++)
{
if (a[i] != ',' && i != a.length - 1)
{
tempNum += a[i];
} else
{
b.push(parseInt(tempNum))
tempNum = '';
}
}
return b;
}
now if you do noCommas('123,345,324234')[2] it would return 324234.

Loop thru a string with numbers and symbols & push to array

I'm trying to loop thru a string with numbers that has a symbol inside, I want the numbers before the symbol to be pushed to an array then the symbol to another array and then get the rest of the numbers after the symbol pushed to a 3rd array.
var myString = "1234*5678";
var number1 = [];
for (i = 0; i < myString.length; i++) {
if (isNaN(myString[i]) === false) {
var firstSet = number1.push(myString[i]);
}
};
var mySymbol = [];
for (j = number1[0]; j < myString.length; j++) {
if (isNaN(myString[j]) === true) {
var mathematics = mySymbol.push(myString[j])
document.write(mySymbol[0])
}
};
when I document.write the "mySymbol" variable it gives the desired result, but when I call the "number1" variable it gives me the numbers from before and after the symbol I only want the numbers before the symbol to be pushed to the array, also how do I write the 3rd loop to get the numbers after the symbol pushed to a new array?

try
var arr=[[],[],[]]
index = 0
"1234*5678".split('').forEach(function(e){
if(parseInt(e)){
arr[index].push(e);
}else{
index ++;
arr[index++].push(e)
}
});
document.write('First Array ' +arr[0] + '<br>');
document.write('Secont Array ' +arr[1] + '<br>');
document.write('Third Array ' +arr[2]);

You could try using:
var myString = '1234*5678';
var resultArr = myString.match(/([a-zA-Z0-9]+)([^a-zA-Z0-9])([a-zA-Z0-9]+)/);
To get the string before symbol:
var myFirstSet = resultArr[1];
To get symbol:
var mySymbol = resultArr[2];
To get the string after symbol:
var mySecondSet = resultArr[3];
To convert each of these three groups into their own arrays:
var result = [];
resultArr
.slice(1)
.forEach(
function(s){
result.push(s
.split('')
.map(
function(n){
return parseInt(n) || n;
}
)
)
}
);

The following code accomplishes the goal:
var str = '1234*5678';
var arr = str.match(/([a-zA-Z0-9]+)|\*/g);
console.log(arr[0], arr[1], arr[2]);
http://jsfiddle.net/hp2ohvzb/

Javascript How to split string by symbols count [duplicate]

As the title says, I've got a string and I want to split into segments of n characters.
For example:
var str = 'abcdefghijkl';
after some magic with n=3, it will become
var arr = ['abc','def','ghi','jkl'];
Is there a way to do this?

var str = 'abcdefghijkl';
console.log(str.match(/.{1,3}/g));
Note: Use {1,3} instead of just {3} to include the remainder for string lengths that aren't a multiple of 3, e.g:
console.log("abcd".match(/.{1,3}/g)); // ["abc", "d"]
A couple more subtleties:
If your string may contain newlines (which you want to count as a character rather than splitting the string), then the . won't capture those. Use /[\s\S]{1,3}/ instead. (Thanks #Mike).
If your string is empty, then match() will return null when you may be expecting an empty array. Protect against this by appending || [].
So you may end up with:
var str = 'abcdef \t\r\nghijkl';
var parts = str.match(/[\s\S]{1,3}/g) || [];
console.log(parts);
console.log(''.match(/[\s\S]{1,3}/g) || []);

If you didn't want to use a regular expression...
var chunks = [];
for (var i = 0, charsLength = str.length; i < charsLength; i += 3) {
chunks.push(str.substring(i, i + 3));
}
jsFiddle.
...otherwise the regex solution is pretty good :)

str.match(/.{3}/g); // => ['abc', 'def', 'ghi', 'jkl']

Building on the previous answers to this question; the following function will split a string (str) n-number (size) of characters.
function chunk(str, size) {
return str.match(new RegExp('.{1,' + size + '}', 'g'));
}
Demo
(function() {
function chunk(str, size) {
return str.match(new RegExp('.{1,' + size + '}', 'g'));
}
var str = 'HELLO WORLD';
println('Simple binary representation:');
println(chunk(textToBin(str), 8).join('\n'));
println('\nNow for something crazy:');
println(chunk(textToHex(str, 4), 8).map(function(h) { return '0x' + h }).join(' '));
// Utiliy functions, you can ignore these.
function textToBin(text) { return textToBase(text, 2, 8); }
function textToHex(t, w) { return pad(textToBase(t,16,2), roundUp(t.length, w)*2, '00'); }
function pad(val, len, chr) { return (repeat(chr, len) + val).slice(-len); }
function print(text) { document.getElementById('out').innerHTML += (text || ''); }
function println(text) { print((text || '') + '\n'); }
function repeat(chr, n) { return new Array(n + 1).join(chr); }
function textToBase(text, radix, n) {
return text.split('').reduce(function(result, chr) {
return result + pad(chr.charCodeAt(0).toString(radix), n, '0');
}, '');
}
function roundUp(numToRound, multiple) {
if (multiple === 0) return numToRound;
var remainder = numToRound % multiple;
return remainder === 0 ? numToRound : numToRound + multiple - remainder;
}
}());
#out {
white-space: pre;
font-size: 0.8em;
}
<div id="out"></div>

If you really need to stick to .split and/or .raplace, then use /(?<=^(?:.{3})+)(?!$)/g
For .split:
var arr = str.split( /(?<=^(?:.{3})+)(?!$)/ )
// [ 'abc', 'def', 'ghi', 'jkl' ]
For .replace:
var replaced = str.replace( /(?<=^(?:.{3})+)(?!$)/g, ' || ' )
// 'abc || def || ghi || jkl'
/(?!$)/ is to not stop at end of the string. Without it's:
var arr = str.split( /(?<=^(?:.{3})+)/ )
// [ 'abc', 'def', 'ghi', 'jkl' ] // is fine
var replaced = str.replace( /(?<=^(.{3})+)/g, ' || ')
// 'abc || def || ghi || jkl || ' // not fine
Ignoring group /(?:...)/ is to prevent duplicating entries in the array. Without it's:
var arr = str.split( /(?<=^(.{3})+)(?!$)/ )
// [ 'abc', 'abc', 'def', 'abc', 'ghi', 'abc', 'jkl' ] // not fine
var replaced = str.replace( /(?<=^(.{3})+)(?!$)/g, ' || ' )
// 'abc || def || ghi || jkl' // is fine

My solution (ES6 syntax):
const source = "8d7f66a9273fc766cd66d1d";
const target = [];
for (
const array = Array.from(source);
array.length;
target.push(array.splice(0,2).join(''), 2));
We could even create a function with this:
function splitStringBySegmentLength(source, segmentLength) {
if (!segmentLength || segmentLength < 1) throw Error('Segment length must be defined and greater than/equal to 1');
const target = [];
for (
const array = Array.from(source);
array.length;
target.push(array.splice(0,segmentLength).join('')));
return target;
}
Then you can call the function easily in a reusable manner:
const source = "8d7f66a9273fc766cd66d1d";
const target = splitStringBySegmentLength(source, 2);
Cheers

const chunkStr = (str, n, acc) => {
if (str.length === 0) {
return acc
} else {
acc.push(str.substring(0, n));
return chunkStr(str.substring(n), n, acc);
}
}
const str = 'abcdefghijkl';
const splittedString = chunkStr(str, 3, []);
Clean solution without REGEX

My favorite answer is gouder hicham's. But I revised it a little so that it makes more sense to me.
let myString = "Able was I ere I saw elba";
let splitString = [];
for (let i = 0; i < myString.length; i = i + 3) {
splitString.push(myString.slice(i, i + 3));
}
console.log(splitString);
Here is a functionalized version of the code.
function stringSplitter(myString, chunkSize) {
let splitString = [];
for (let i = 0; i < myString.length; i = i + chunkSize) {
splitString.push(myString.slice(i, i + chunkSize));
}
return splitString;
}
And the function's use:
let myString = "Able was I ere I saw elba";
let mySplitString = stringSplitter(myString, 3);
console.log(mySplitString);
And it's result:
>(9) ['Abl', 'e w', 'as ', 'I e', 're ', 'I s', 'aw ', 'elb', 'a']

try this simple code and it will work like magic !
let letters = "abcabcabcabcabc";
// we defined our variable or the name whatever
let a = -3;
let finalArray = [];
for (let i = 0; i <= letters.length; i += 3) {
finalArray.push(letters.slice(a, i));
a += 3;
}
// we did the shift method cause the first element in the array will be just a string "" so we removed it
finalArray.shift();
// here the final result
console.log(finalArray);

var str = 'abcdefghijkl';
var res = str.match(/.../g)
console.log(res)
here number of dots determines how many text you want in each word.

function chunk(er){
return er.match(/.{1,75}/g).join('\n');
}
Above function is what I use for Base64 chunking. It will create a line break ever 75 characters.

Here we intersperse a string with another string every n characters:
export const intersperseString = (n: number, intersperseWith: string, str: string): string => {
let ret = str.slice(0,n), remaining = str;
while (remaining) {
let v = remaining.slice(0, n);
remaining = remaining.slice(v.length);
ret += intersperseWith + v;
}
return ret;
};
if we use the above like so:
console.log(splitString(3,'|', 'aagaegeage'));
we get:
aag|aag|aeg|eag|e
and here we do the same, but push to an array:
export const sperseString = (n: number, str: string): Array<string> => {
let ret = [], remaining = str;
while (remaining) {
let v = remaining.slice(0, n);
remaining = remaining.slice(v.length);
ret.push(v);
}
return ret;
};
and then run it:
console.log(sperseString(5, 'foobarbaztruck'));
we get:
[ 'fooba', 'rbazt', 'ruck' ]
if someone knows of a way to simplify the above code, lmk, but it should work fine for strings.

Coming a little later to the discussion but here a variation that's a little faster than the substring + array push one.
// substring + array push + end precalc
var chunks = [];
for (var i = 0, e = 3, charsLength = str.length; i < charsLength; i += 3, e += 3) {
chunks.push(str.substring(i, e));
}
Pre-calculating the end value as part of the for loop is faster than doing the inline math inside substring. I've tested it in both Firefox and Chrome and they both show speedup.
You can try it here

Here's a way to do it without regular expressions or explicit loops, although it's stretching the definition of a one liner a bit:
const input = 'abcdefghijlkm';
// Change `3` to the desired split length.
const output = input.split('').reduce((s, c) => {
let l = s.length-1;
(s[l] && s[l].length < 3) ? s[l] += c : s.push(c);
return s;
}, []);
console.log(output); // output: [ 'abc', 'def', 'ghi', 'jlk', 'm' ]
It works by splitting the string into an array of individual characters, then using Array.reduce to iterate over each character. Normally reduce would return a single value, but in this case the single value happens to be an array, and as we pass over each character we append it to the last item in that array. Once the last item in the array reaches the target length, we append a new array item.

Some clean solution without using regular expressions:
/**
* Create array with maximum chunk length = maxPartSize
* It work safe also for shorter strings than part size
**/
function convertStringToArray(str, maxPartSize){
const chunkArr = [];
let leftStr = str;
do {
chunkArr.push(leftStr.substring(0, maxPartSize));
leftStr = leftStr.substring(maxPartSize, leftStr.length);
} while (leftStr.length > 0);
return chunkArr;
};
Usage example - https://jsfiddle.net/maciejsikora/b6xppj4q/.
I also tried to compare my solution to regexp one which was chosen as right answer. Some test can be found on jsfiddle - https://jsfiddle.net/maciejsikora/2envahrk/. Tests are showing that both methods have similar performance, maybe on first look regexp solution is little bit faster, but judge it Yourself.

var b1 = "";
function myFunction(n) {
if(str.length>=3){
var a = str.substring(0,n);
b1 += a+ "\n"
str = str.substring(n,str.length)
myFunction(n)
}
else{
if(str.length>0){
b1 += str
}
console.log(b1)
}
}
myFunction(4)

function str_split(string, length = 1) {
if (0 >= length)
length = 1;
if (length == 1)
return string.split('');
var string_size = string.length;
var result = [];
for (let i = 0; i < string_size / length; i++)
result[i] = string.substr(i * length, length);
return result;
}
str_split(str, 3)
Benchmark: http://jsben.ch/HkjlU (results differ per browser)
Results (Chrome 104)

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