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Merge strings in 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('');
}

How to compare strings in an array: Javascript

I have an array which looks like
var arr = ["a|c", "a|e", "x|z"];
for(var x in arr){
var appsplit = x.split("|");
}
If the first value(ex: a) in the elements matches then it should combine the values
Ex: output
ace
xz
Please advice how this approach can be done.

You are testing everyone's reading comprehension with that riddle.
var pairs = {};
var arr = ["a|c", "a|e", "x|z"];
for(var x in arr)
{
var appsplit = arr[x].split("|");
if(pairs[appsplit[0]] !== "undefined")
{
pairs[appsplit[0]] = pairs[appsplit[0]] + appsplit[1];
}
else
{
pairs[appsplit[0]] = appsplit[1];
}
}
var matches = [];
for(var x in pairs)
{
matches.push(x + pairs[x]);
}
console.log(matches);
We need to map out the arr elements in this object called pairs. The first value in your split would be the key and the second value is appended (or assigned if it's the first match to the key)
You made an error of splitting x, but you are only splitting the index of the element, not the actual value of the element. arr[x] is the actual value, where x specifies the index in the array.
After we've gone through your arr, we can now merge the key with the values. Your output is contained in matches where the key in each pair is prepended to the value of the key's pair.

Some simple code that would to the trick here.
var arr = ["a|c", "a|e", "x|z", "c|b", "z|e", "c|a"];
var resultObj = {};
arr.forEach(function(element, index){
var array = element.split('|');
if(array.length!==2){
console.log("skipping, invalid input data", element);
} else {
var firstLetter = array[0];
var secondLetter = array[1];
if(resultObj[firstLetter]){
resultObj[firstLetter].push(secondLetter);
} else {
resultObj[firstLetter]=[secondLetter];
}
}
});
Object.keys(resultObj).forEach(function(key){
console.log(key + "," + resultObj[key]);
});

You can use .reduce(), Set to not accumulate duplicate values, .some() to check if previous array contains value in current array, .map(), Array.from() and .join() to convert array to string
var arr = ["a|c", "a|e", "x|z"];
var res = arr.reduce(function(a, b) {
var curr = b.split("|");
var set = new Set;
for (let prop of curr) set.add(prop);
if (!a.length) {
a.push(set)
} else {
for (prop of a) {
if (curr.some(function(el) {
return prop.has(el)
})) {
for (el of curr) {
prop.add(el)
}
} else {
for (let prop of curr) set.add(prop);
a.push(set)
}
}
}
return a
}, []).map(function(m) {
return Array.from([...m], function(el) {
return el
}).join("")
});
console.log(res);

I feel like this can be done more elegantly, but I didn't have time to streamline it. :) The below code will do what you want, though:
var aStartArray = **ARRAY_VALUE_HERE**;
var aSplitResultStrings = [];
// step through each element in the array
for (var i = 0, iSALength = aStartArray.length; i < iSALength; i++) {
// split the values for the current array element
var aSplitVal = aStartArray[i].split("|");
var bStringDoesNotExist = true;
// loop through the "result strings" array
for (var j = 0, iSRSLength = aSplitResultStrings.length; j < iSRSLength; j++) {
// if the first letter from the array element = the first letter of the current "result string" . . .
if (aSplitResultStrings[j].charAt(0) === aSplitVal[0]) {
// append the second letter of the array value to the current result string
aSplitResultStrings[j] = aSplitResultStrings[j] + aSplitVal[1];
// indicate that a match has been found and exit the "result string" loop
bStringDoesNotExist = false;
break;
}
}
// if there are no result strings that start with the first letter of the array value . . .
if (bStringDoesNotExist) {
// concatenate the two values in the current array value and add them as a new "result string"
aSplitResultStrings.push(aSplitVal[0] + aSplitVal[1]);
}
}
Using these arrays, the results are:
aStartArray = ["a|c", "a|e", "x|z"] //results in:
aSplitResultStrings = ["ace", "xz"]
aStartArray = ["a|b", "a|c", "a|d", "a|e", "x|y", "x|z"] //results in:
aSplitResultStrings = ["abcde", "xyz"]
aStartArray = ["a|b", "d|e", "d|f", "x|y", "g|h", "g|i", "m|n", "g|j", "a|c", "x|z"] //results in:
aSplitResultStrings = ["abc", "def", "xyz", "ghij", "mn"]
As I said, this could be more elegant (for example, you could probably use Map to make iterating through the "result strings" easier), but this makes the steps pretty clear and should get you going down the right path towards a final solution.

find the difference use javascript

this is a leetcode question.
Given two strings s and t which consist of only lowercase letters.
String t is generated by random shuffling string s and then add one more letter at a random position.
Find the letter that was added in t.
https://leetcode.com/problems/find-the-difference/
I'm trying to think a hash table way but seems I m wrong.
var findTheDifference = function(s, t) {
var hashTable = {};
var array = s.split('');
array.forEach(function (element) {
hashTable[element] = element;
});
for( var i = 0; i < t.length; i++) {
if(!hashTable.hasOwnProperty(t.charAt(i))) {
return t.charAt(i);
}
}
};
this wrong code can pass the sample Input:
Input:
s = "abcd"
t = "abcde"
Output:
e
but for large strings will be wrong
Input :"ymbgaraibkfmvocpizdydugvalagaivdbfsfbepeyccqfepzvtpyxtbadkhmwmoswrcxnargtlswqemafandgkmydtimuzvjwxvlfwlhvkrgcsithaqlcvrihrwqkpjdhgfgreqoxzfvhjzojhghfwbvpfzectwwhexthbsndovxejsntmjihchaotbgcysfdaojkjldprwyrnischrgmtvjcorypvopfmegizfkvudubnejzfqffvgdoxohuinkyygbdzmshvyqyhsozwvlhevfepdvafgkqpkmcsikfyxczcovrmwqxxbnhfzcjjcpgzjjfateajnnvlbwhyppdleahgaypxidkpwmfqwqyofwdqgxhjaxvyrzupfwesmxbjszolgwqvfiozofncbohduqgiswuiyddmwlwubetyaummenkdfptjczxemryuotrrymrfdxtrebpbjtpnuhsbnovhectpjhfhahbqrfbyxggobsweefcwxpqsspyssrmdhuelkkvyjxswjwofngpwfxvknkjviiavorwyfzlnktmfwxkvwkrwdcxjfzikdyswsuxegmhtnxjraqrdchaauazfhtklxsksbhwgjphgbasfnlwqwukprgvihntsyymdrfovaszjywuqygpvjtvlsvvqbvzsmgweiayhlubnbsitvfxawhfmfiatxvqrcwjshvovxknnxnyyfexqycrlyksderlqarqhkxyaqwlwoqcribumrqjtelhwdvaiysgjlvksrfvjlcaiwrirtkkxbwgicyhvakxgdjwnwmubkiazdjkfmotglclqndqjxethoutvjchjbkoasnnfbgrnycucfpeovruguzumgmgddqwjgdvaujhyqsqtoexmnfuluaqbxoofvotvfoiexbnprrxptchmlctzgqtkivsilwgwgvpidpvasurraqfkcmxhdapjrlrnkbklwkrvoaziznlpor"
"qhxepbshlrhoecdaodgpousbzfcqjxulatciapuftffahhlmxbufgjuxstfjvljybfxnenlacmjqoymvamphpxnolwijwcecgwbcjhgdybfffwoygikvoecdggplfohemfypxfsvdrseyhmvkoovxhdvoavsqqbrsqrkqhbtmgwaurgisloqjixfwfvwtszcxwktkwesaxsmhsvlitegrlzkvfqoiiwxbzskzoewbkxtphapavbyvhzvgrrfriddnsrftfowhdanvhjvurhljmpxvpddxmzfgwwpkjrfgqptrmumoemhfpojnxzwlrxkcafvbhlwrapubhveattfifsmiounhqusvhywnxhwrgamgnesxmzliyzisqrwvkiyderyotxhwspqrrkeczjysfujvovsfcfouykcqyjoobfdgnlswfzjmyucaxuaslzwfnetekymrwbvponiaojdqnbmboldvvitamntwnyaeppjaohwkrisrlrgwcjqqgxeqerjrbapfzurcwxhcwzugcgnirkkrxdthtbmdqgvqxilllrsbwjhwqszrjtzyetwubdrlyakzxcveufvhqugyawvkivwonvmrgnchkzdysngqdibhkyboyftxcvvjoggecjsajbuqkjjxfvynrjsnvtfvgpgveycxidhhfauvjovmnbqgoxsafknluyimkczykwdgvqwlvvgdmufxdypwnajkncoynqticfetcdafvtqszuwfmrdggifokwmkgzuxnhncmnsstffqpqbplypapctctfhqpihavligbrutxmmygiyaklqtakdidvnvrjfteazeqmbgklrgrorudayokxptswwkcircwuhcavhdparjfkjypkyxhbgwxbkvpvrtzjaetahmxevmkhdfyidhrdeejapfbafwmdqjqszwnwzgclitdhlnkaiyldwkwwzvhyorgbysyjbxsspnjdewjxbhpsvj"
Thanks for any suggestion~~~~

One approach would be to sort the strings, then find where the first difference between them is:
var str = "1122334477422";
var str2 = "15122332247744";
var sorted = str.split('').sort();
var sorted2 = str2.split('').sort()
for(var i = 0; i< sorted2.length; i++){
if(i == sorted2.length || sorted[i] != sorted2[i]){
alert(sorted2[i]);
break;
}
}

You could use a hash table for counting. Add for every letter in the original string one and subtract one for every letter in the manipulated string. Then take only the hashes with nonempty count.
var data1 = "ymbgaraibkfmvocpizdydugvalagaivdbfsfbepeyccqfepzvtpyxtbadkhmwmoswrcxnargtlswqemafandgkmydtimuzvjwxvlfwlhvkrgcsithaqlcvrihrwqkpjdhgfgreqoxzfvhjzojhghfwbvpfzectwwhexthbsndovxejsntmjihchaotbgcysfdaojkjldprwyrnischrgmtvjcorypvopfmegizfkvudubnejzfqffvgdoxohuinkyygbdzmshvyqyhsozwvlhevfepdvafgkqpkmcsikfyxczcovrmwqxxbnhfzcjjcpgzjjfateajnnvlbwhyppdleahgaypxidkpwmfqwqyofwdqgxhjaxvyrzupfwesmxbjszolgwqvfiozofncbohduqgiswuiyddmwlwubetyaummenkdfptjczxemryuotrrymrfdxtrebpbjtpnuhsbnovhectpjhfhahbqrfbyxggobsweefcwxpqsspyssrmdhuelkkvyjxswjwofngpwfxvknkjviiavorwyfzlnktmfwxkvwkrwdcxjfzikdyswsuxegmhtnxjraqrdchaauazfhtklxsksbhwgjphgbasfnlwqwukprgvihntsyymdrfovaszjywuqygpvjtvlsvvqbvzsmgweiayhlubnbsitvfxawhfmfiatxvqrcwjshvovxknnxnyyfexqycrlyksderlqarqhkxyaqwlwoqcribumrqjtelhwdvaiysgjlvksrfvjlcaiwrirtkkxbwgicyhvakxgdjwnwmubkiazdjkfmotglclqndqjxethoutvjchjbkoasnnfbgrnycucfpeovruguzumgmgddqwjgdvaujhyqsqtoexmnfuluaqbxoofvotvfoiexbnprrxptchmlctzgqtkivsilwgwgvpidpvasurraqfkcmxhdapjrlrnkbklwkrvoaziznlpor",
data2 = "qhxepbshlrhoecdaodgpousbzfcqjxulatciapuftffahhlmxbufgjuxstfjvljybfxnenlacmjqoymvamphpxnolwijwcecgwbcjhgdybfffwoygikvoecdggplfohemfypxfsvdrseyhmvkoovxhdvoavsqqbrsqrkqhbtmgwaurgisloqjixfwfvwtszcxwktkwesaxsmhsvlitegrlzkvfqoiiwxbzskzoewbkxtphapavbyvhzvgrrfriddnsrftfowhdanvhjvurhljmpxvpddxmzfgwwpkjrfgqptrmumoemhfpojnxzwlrxkcafvbhlwrapubhveattfifsmiounhqusvhywnxhwrgamgnesxmzliyzisqrwvkiyderyotxhwspqrrkeczjysfujvovsfcfouykcqyjoobfdgnlswfzjmyucaxuaslzwfnetekymrwbvponiaojdqnbmboldvvitamntwnyaeppjaohwkrisrlrgwcjqqgxeqerjrbapfzurcwxhcwzugcgnirkkrxdthtbmdqgvqxilllrsbwjhwqszrjtzyetwubdrlyakzxcveufvhqugyawvkivwonvmrgnchkzdysngqdibhkyboyftxcvvjoggecjsajbuqkjjxfvynrjsnvtfvgpgveycxidhhfauvjovmnbqgoxsafknluyimkczykwdgvqwlvvgdmufxdypwnajkncoynqticfetcdafvtqszuwfmrdggifokwmkgzuxnhncmnsstffqpqbplypapctctfhqpihavligbrutxmmygiyaklqtakdidvnvrjfteazeqmbgklrgrorudayokxptswwkcircwuhcavhdparjfkjypkyxhbgwxbkvpvrtzjaetahmxevmkhdfyidhrdeejapfbafwmdqjqszwnwzgclitdhlnkaiyldwkwwzvhyorgbysyjbxsspnjdewjxbhpsvj",
hash = Object.create(null),
count = function (a) { hash[a] = (hash[a] || 0) + this; },
result;
data1.split('').forEach(count, 1);
data2.split('').forEach(count, -1);
result = Object.keys(hash).filter(function (k) { return hash[k]; });
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.

How to find the string that matches in array?

I would like to get the full string element from an array that matches multiple substrings in no particular order. If more than one match, an exception should be thrown.
var thisArray = [ '/something_else/', '/and_something_else/', '/and_something_else_here/'];
var thisMatch = [ 'some', 'and', 'here'];
var matchingElement = new RegExp(thisArray , thisMatch); // Not sure about this
What I want is for matchineElement to contain the string "and_something_else_here" after the regular expression has executed.

You could do something like this:
var thisArray = [ '/something_else/', '/and_something_else/', '/and_something_else_here/'];
var thisMatch = [ 'some', 'and', 'here'];
function matchElements(arr, arrMatch) {
var tmpArr;
arrMatch.forEach(function(el, i, a) {
tmpArr = arr.filter(function(str) {
return str.indexOf(el) !== -1;
});
});
if (tmpArr.length > 1) {
throw ("Hey, too many matches");
} else {
return tmpArr[0];
}
}
console.log(matchElements(thisArray, thisMatch));
JSFiddle: http://jsfiddle.net/Le53y7ee/
Explanation:
The function goes through every element in the array containing substrings and filters main array keeping only strings that match. After the loop is done the array should contain only string(s) that matched all required substrings.

A regexp that matches a string containing all of a set of substrings looks like:
^(?=.*?string1)(?=.*?string2)(?=.*?string3).*$
So you just need to convert your thisMatch array into such a regular expression.
var regexp = new RegExp('^' + thisMatch.map(function(x) {
return '(?=.*?' + x + ')';
}).join('') + '.*$');
Then you can find all the matches with:
var matchingElements = thisArray.filter(function(x) {
return regexp.test(x);
});
if (matchingElements.length != 1) {
throw new Error('Single match not found');
} else {
matchingElement = matchingElements[0];
}
DEMO

Try
var matchingElement = thisArray.filter(function(val, key) {
var value = val.split(/[^a-z]/).filter(String).join(" ");
// if `.test()` returns `true` three times at `value`
return new RegExp(this[0]).test(value)
&& new RegExp(this[1]).test(value)
&& new RegExp(this[2]).test(value)
? val
: null
}.bind(thisMatch))[0].replace(/\//g,"");)
var thisArray = [ '/something_else/', '/and_something_else/', '/and_something_else_here/'];
var thisMatch = [ 'some', 'and', 'here'];
var matchingElement = thisArray.filter(function(val, key) {
var value = val.split(/[^a-z]/).filter(String).join(" ");
// if `.test()` returns `true` three times at `value`
return new RegExp(this[0]).test(value)
&& new RegExp(this[1]).test(value)
&& new RegExp(this[2]).test(value)
? val
: null
}.bind(thisMatch))[0].replace(/\//g,"");
document.write(matchingElement)

Take those slashes off of both sides of your Strings in those Arrays. Then use the arrayMatch function below, and loop over your indexes to get the results of thisArray, like:
function arrayMatch(yourArray, wordMatchArray){
var ix = [], c = wordMatchArray.length;
for(var i=0,l=yourArray.length; i<l; i++){
var m = 0;
for(var n=0; n<c; n++){
if(yourArray[i].match(new RegExp(wordMatchArray[n])))m++;
if(c === m)ix.push(i);
}
}
if(!ix[0]){
return false;
}
return ix;
}
var indexes = arrayMatch(thisArray, thisMatch);
for(var i=0,l=indexes.length; i<l; i++){
var getMatch = thisArray[indexes[i]];
}