I'm trying to figure out how to remove every second character (starting from the first one) from a string in Javascript.
For example, the string "This is a test!" should become "hsi etTi sats!"
I also want to save every deleted character into another array.
I have tried using replace method and splice method, but wasn't able to get them to work properly. Mostly because replace only replaces the first character.
function encrypt(text, n) {
if (text === "NULL") return n;
if (n <= 0) return text;
var encArr = [];
var newString = text.split("");
var j = 0;
for (var i = 0; i < text.length; i += 2) {
encArr[j++] = text[i];
newString.splice(i, 1); // this line doesn't work properly
}
}
You could reduce the characters of the string and group them to separate arrays using the % operator. Use destructuring to get the 2D array returned to separate variables
let str = "This is a test!";
const [even, odd] = [...str].reduce((r,char,i) => (r[i%2].push(char), r), [[],[]])
console.log(odd.join(''))
console.log(even.join(''))
Using a for loop:
let str = "This is a test!",
odd = [],
even = [];
for (var i = 0; i < str.length; i++) {
i % 2 === 0
? even.push(str[i])
: odd.push(str[i])
}
console.log(odd.join(''))
console.log(even.join(''))
It would probably be easier to use a regular expression and .replace: capture two characters in separate capturing groups, add the first character to a string, and replace with the second character. Then, you'll have first half of the output you need in one string, and the second in another: just concatenate them together and return:
function encrypt(text) {
let removedText = '';
const replacedText1 = text.replace(/(.)(.)?/g, (_, firstChar, secondChar) => {
// in case the match was at the end of the string,
// and the string has an odd number of characters:
if (!secondChar) secondChar = '';
// remove the firstChar from the string, while adding it to removedText:
removedText += firstChar;
return secondChar;
});
return replacedText1 + removedText;
}
console.log(encrypt('This is a test!'));
Pretty simple with .reduce() to create the two arrays you seem to want.
function encrypt(text) {
return text.split("")
.reduce(({odd, even}, c, i) =>
i % 2 ? {odd: [...odd, c], even} : {odd, even: [...even, c]}
, {odd: [], even: []})
}
console.log(encrypt("This is a test!"));
They can be converted to strings by using .join("") if you desire.
I think you were on the right track. What you missed is replace is using either a string or RegExp.
The replace() method returns a new string with some or all matches of a pattern replaced by a replacement. The pattern can be a string or a RegExp, and the replacement can be a string or a function to be called for each match. If pattern is a string, only the first occurrence will be replaced.
Source: String.prototype.replace()
If you are replacing a value (and not a regular expression), only the first instance of the value will be replaced. To replace all occurrences of a specified value, use the global (g) modifier
Source: JavaScript String replace() Method
So my suggestion would be to continue still with replace and pass the right RegExp to the function, I guess you can figure out from this example - this removes every second occurrence for char 't':
let count = 0;
let testString = 'test test test test';
console.log('original', testString);
// global modifier in RegExp
let result = testString.replace(/t/g, function (match) {
count++;
return (count % 2 === 0) ? '' : match;
});
console.log('removed', result);
like this?
var text = "This is a test!"
var result = ""
var rest = ""
for(var i = 0; i < text.length; i++){
if( (i%2) != 0 ){
result += text[i]
} else{
rest += text[i]
}
}
console.log(result+rest)
Maybe with split, filter and join:
const remaining = myString.split('').filter((char, i) => i % 2 !== 0).join('');
const deleted = myString.split('').filter((char, i) => i % 2 === 0).join('');
You could take an array and splice and push each second item to the end of the array.
function encrypt(string) {
var array = [...string],
i = 0,
l = array.length >> 1;
while (i <= l) array.push(array.splice(i++, 1)[0]);
return array.join('');
}
console.log(encrypt("This is a test!"));
function encrypt(text) {
text = text.split("");
var removed = []
var encrypted = text.filter((letter, index) => {
if(index % 2 == 0){
removed.push(letter)
return false;
}
return true
}).join("")
return {
full: encrypted + removed.join(""),
encrypted: encrypted,
removed: removed
}
}
console.log(encrypt("This is a test!"))
Splice does not work, because if you remove an element from an array in for loop indexes most probably will be wrong when removing another element.
I don't know how much you care about performance, but using regex is not very efficient.
Simple test for quite a long string shows that using filter function is on average about 3 times faster, which can make quite a difference when performed on very long strings or on many, many shorts ones.
function test(func, n){
var text = "";
for(var i = 0; i < n; ++i){
text += "a";
}
var start = new Date().getTime();
func(text);
var end = new Date().getTime();
var time = (end-start) / 1000.0;
console.log(func.name, " took ", time, " seconds")
return time;
}
function encryptREGEX(text) {
let removedText = '';
const replacedText1 = text.replace(/(.)(.)?/g, (_, firstChar, secondChar) => {
// in case the match was at the end of the string,
// and the string has an odd number of characters:
if (!secondChar) secondChar = '';
// remove the firstChar from the string, while adding it to removedText:
removedText += firstChar;
return secondChar;
});
return replacedText1 + removedText;
}
function encrypt(text) {
text = text.split("");
var removed = "";
var encrypted = text.filter((letter, index) => {
if(index % 2 == 0){
removed += letter;
return false;
}
return true
}).join("")
return encrypted + removed
}
var timeREGEX = test(encryptREGEX, 10000000);
var timeFilter = test(encrypt, 10000000);
console.log("Using filter is faster ", timeREGEX/timeFilter, " times")
Using actually an array for storing removed letters and then joining them is much more efficient, than using a string and concatenating letters to it.
I changed an array to string in filter solution to make it the same like in regex solution, so they are more comparable.
I'm looking for [a, b, c, "d, e, f", g, h]to turn into an array of 6 elements: a, b, c, "d,e,f", g, h. I'm trying to do this through Javascript. This is what I have so far:
str = str.split(/,+|"[^"]+"/g);
But right now it's splitting out everything that's in the double-quotes, which is incorrect.
Edit: Okay sorry I worded this question really poorly. I'm being given a string not an array.
var str = 'a, b, c, "d, e, f", g, h';
And I want to turn that into an array using something like the "split" function.
Here's what I would do.
var str = 'a, b, c, "d, e, f", g, h';
var arr = str.match(/(".*?"|[^",\s]+)(?=\s*,|\s*$)/g);
/* will match:
(
".*?" double quotes + anything but double quotes + double quotes
| OR
[^",\s]+ 1 or more characters excl. double quotes, comma or spaces of any kind
)
(?= FOLLOWED BY
\s*, 0 or more empty spaces and a comma
| OR
\s*$ 0 or more empty spaces and nothing else (end of string)
)
*/
arr = arr || [];
// this will prevent JS from throwing an error in
// the below loop when there are no matches
for (var i = 0; i < arr.length; i++) console.log('arr['+i+'] =',arr[i]);
regex: /,(?=(?:(?:[^"]*"){2})*[^"]*$)/
const input_line = '"2C95699FFC68","201 S BOULEVARDRICHMOND, VA 23220","8299600062754882","2018-09-23"'
let my_split = input_line.split(/,(?=(?:(?:[^"]*"){2})*[^"]*$)/)[4]
Output:
my_split[0]: "2C95699FFC68",
my_split[1]: "201 S BOULEVARDRICHMOND, VA 23220",
my_split[2]: "8299600062754882",
my_split[3]: "2018-09-23"
Reference following link for an explanation: regexr.com/44u6o
Here is a JavaScript function to do it:
function splitCSVButIgnoreCommasInDoublequotes(str) {
//split the str first
//then merge the elments between two double quotes
var delimiter = ',';
var quotes = '"';
var elements = str.split(delimiter);
var newElements = [];
for (var i = 0; i < elements.length; ++i) {
if (elements[i].indexOf(quotes) >= 0) {//the left double quotes is found
var indexOfRightQuotes = -1;
var tmp = elements[i];
//find the right double quotes
for (var j = i + 1; j < elements.length; ++j) {
if (elements[j].indexOf(quotes) >= 0) {
indexOfRightQuotes = j;
break;
}
}
//found the right double quotes
//merge all the elements between double quotes
if (-1 != indexOfRightQuotes) {
for (var j = i + 1; j <= indexOfRightQuotes; ++j) {
tmp = tmp + delimiter + elements[j];
}
newElements.push(tmp);
i = indexOfRightQuotes;
}
else { //right double quotes is not found
newElements.push(elements[i]);
}
}
else {//no left double quotes is found
newElements.push(elements[i]);
}
}
return newElements;
}
Here's a non-regex one that assumes doublequotes will come in pairs:
function splitCsv(str) {
return str.split(',').reduce((accum,curr)=>{
if(accum.isConcatting) {
accum.soFar[accum.soFar.length-1] += ','+curr
} else {
accum.soFar.push(curr)
}
if(curr.split('"').length % 2 == 0) {
accum.isConcatting= !accum.isConcatting
}
return accum;
},{soFar:[],isConcatting:false}).soFar
}
console.log(splitCsv('asdf,"a,d",fdsa'),' should be ',['asdf','"a,d"','fdsa'])
console.log(splitCsv(',asdf,,fds,'),' should be ',['','asdf','','fds',''])
console.log(splitCsv('asdf,"a,,,d",fdsa'),' should be ',['asdf','"a,,,d"','fdsa'])
This works well for me. (I used semicolons so the alert message would show the difference between commas added when turning the array into a string and the actual captured values.)
REGEX
/("[^"]*")|[^;]+/
var str = 'a; b; c; "d; e; f"; g; h; "i"';
var array = str.match(/("[^"]*")|[^;]+/g);
alert(array);
Here's the regex we're using to extract valid arguments from a comma-separated argument list, supporting double-quoted arguments. It works for the outlined edge cases. E.g.
doesn't include quotes in the matches
works with white spaces in matches
works with empty fields
(?<=")[^"]+?(?="(?:\s*?,|\s*?$))|(?<=(?:^|,)\s*?)(?:[^,"\s][^,"]*[^,"\s])|(?:[^,"\s])(?![^"]*?"(?:\s*?,|\s*?$))(?=\s*?(?:,|$))
Proof: https://regex101.com/r/UL8kyy/3/tests (Note: currently only works in Chrome because the regex uses lookbehinds which are only supported in ECMA2018)
According to our guidelines it avoids non-capturing groups and greedy matching.
I'm sure it can be simplified, I'm open to suggestions / additional test cases.
For anyone interested, the first part matches double-quoted, comma-delimited arguments:
(?<=")[^"]+?(?="(?:\s*?,|\s*?$))
And the second part matches comma-delimited arguments by themselves:
(?<=(?:^|,)\s*?)(?:[^,"\s][^,"]*[^,"\s])|(?:[^,"\s])(?![^"]*?"(?:\s*?,|\s*?$))(?=\s*?(?:,|$))
I almost liked the accepted answer, but it didn't parse the space correctly, and/or it left the double quotes untrimmed, so here is my function:
/**
* Splits the given string into components, and returns the components array.
* Each component must be separated by a comma.
* If the component contains one or more comma(s), it must be wrapped with double quotes.
* The double quote must not be used inside components (replace it with a special string like __double__quotes__ for instance, then transform it again into double quotes later...).
*
* https://stackoverflow.com/questions/11456850/split-a-string-by-commas-but-ignore-commas-within-double-quotes-using-javascript
*/
function splitComponentsByComma(str){
var ret = [];
var arr = str.match(/(".*?"|[^",]+)(?=\s*,|\s*$)/g);
for (let i in arr) {
let element = arr[i];
if ('"' === element[0]) {
element = element.substr(1, element.length - 2);
} else {
element = arr[i].trim();
}
ret.push(element);
}
return ret;
}
console.log(splitComponentsByComma('Hello World, b, c, "d, e, f", c')); // [ 'Hello World', 'b', 'c', 'd, e, f', 'c' ]
Parse any CSV or CSV-String code based on TYPESCRIPT
public parseCSV(content:string):any[string]{
return content.split("\n").map(ar=>ar.split(/,(?=(?:(?:[^"]*"){2})*[^"]*$)/).map(refi=>refi.replace(/[\x00-\x08\x0E-\x1F\x7F-\uFFFF]/g, "").trim()));
}
var str='"abc",jkl,1000,qwerty6000';
parseCSV(str);
output :
[
"abc","jkl","1000","qwerty6000"
]
I know it's a bit long, but here's my take:
var sample="[a, b, c, \"d, e, f\", g, h]";
var inQuotes = false, items = [], currentItem = '';
for(var i = 0; i < sample.length; i++) {
if (sample[i] == '"') {
inQuotes = !inQuotes;
if (!inQuotes) {
if (currentItem.length) items.push(currentItem);
currentItem = '';
}
continue;
}
if ((/^[\"\[\]\,\s]$/gi).test(sample[i]) && !inQuotes) {
if (currentItem.length) items.push(currentItem);
currentItem = '';
continue;
}
currentItem += sample[i];
}
if (currentItem.length) items.push(currentItem);
console.log(items);
As a side note, it will work both with, and without the braces in the start and end.
This takes a csv file one line at a time and spits back an array with commas inside speech marks intact. if there are no speech marks detected it just .split(",")s as normal... could probs replace that second loop with something but it does the job as is
function parseCSVLine(str){
if(str.indexOf("\"")>-1){
var aInputSplit = str.split(",");
var aOutput = [];
var iMatch = 0;
//var adding = 0;
for(var i=0;i<aInputSplit.length;i++){
if(aInputSplit[i].indexOf("\"")>-1){
var sWithCommas = aInputSplit[i];
for(var z=i;z<aInputSplit.length;z++){
if(z !== i && aInputSplit[z].indexOf("\"") === -1){
sWithCommas+= ","+aInputSplit[z];
}else if(z !== i && aInputSplit[z].indexOf("\"") > -1){
sWithCommas+= ","+aInputSplit[z];
sWithCommas.replace(new RegExp("\"", 'g'), "");
aOutput.push(sWithCommas);
i=z;
z=aInputSplit.length+1;
iMatch++;
}
if(z === aInputSplit.length-1){
if(iMatch === 0){
aOutput.push(aInputSplit[z]);
}
iMatch = 0;
}
}
}else{
aOutput.push(aInputSplit[i]);
}
}
return aOutput
}else{
return str.split(",")
}
}
Use the npm library csv-string to parse the strings instead of split: https://www.npmjs.com/package/csv-string
This will handle the empty entries
Something like a stack should do the trick. Here I vaguely use marker boolean as stack (just getting my purpose served with it).
var str = "a,b,c,blah\"d,=,f\"blah,\"g,h,";
var getAttributes = function(str){
var result = [];
var strBuf = '';
var start = 0 ;
var marker = false;
for (var i = 0; i< str.length; i++){
if (str[i] === '"'){
marker = !marker;
}
if (str[i] === ',' && !marker){
result.push(str.substr(start, i - start));
start = i+1;
}
}
if (start <= str.length){
result.push(str.substr(start, i - start));
}
return result;
};
console.log(getAttributes(str));
jsfiddle setting image code output image
The code works if your input string in the format of stringTocompare.
Run the code on https://jsfiddle.net/ to see output for fiddlejs setting.
Please refer to the screenshot.
You can either use split function for the same for the code below it and tweak the code according to you need.
Remove the bold or word with in ** from the code if you dont want to have comma after split attach=attach**+","**+actualString[t+1].
var stringTocompare='"Manufacturer","12345","6001","00",,"Calfe,eto,lin","Calfe,edin","4","20","10","07/01/2018","01/01/2006",,,,,,,,"03/31/2004"';
console.log(stringTocompare);
var actualString=stringTocompare.split(',');
console.log("Before");
for(var i=0;i<actualString.length;i++){
console.log(actualString[i]);
}
//var actualString=stringTocompare.split(/,(?=(?:(?:[^"]*"){2})*[^"]*$)/);
for(var i=0;i<actualString.length;i++){
var flag=0;
var x=actualString[i];
if(x!==null)
{
if(x[0]=='"' && x[x.length-1]!=='"'){
var p=0;
var t=i;
var b=i;
for(var k=i;k<actualString.length;k++){
var y=actualString[k];
if(y[y.length-1]!=='"'){
p++;
}
if(y[y.length-1]=='"'){
flag=1;
}
if(flag==1)
break;
}
var attach=actualString[t];
for(var s=p;s>0;s--){
attach=attach+","+actualString[t+1];
t++;
}
actualString[i]=attach;
actualString.splice(b+1,p);
}
}
}
console.log("After");
for(var i=0;i<actualString.length;i++){
console.log(actualString[i]);
}
[1]: https://i.stack.imgur.com/3FcxM.png
I solved this with a simple parser.
It simply goes through the string char by char, splitting off a segment when it finds the split_char (e.g. comma), but also has an on/off flag which is switched by finding the encapsulator_char (e.g. quote). It doesn't require the encapsulator to be at the start of the field/segment (a,b","c,d would produce 3 segments, with 'b","c' as the second), but it should work for a well formed CSV with escaped encapsulator chars.
function split_except_within(text, split_char, encapsulator_char, escape_char) {
var start = 0
var encapsulated = false
var fields = []
for (var c = 0; c < text.length; c++) {
var char = text[c]
if (char === split_char && ! encapsulated) {
fields.push(text.substring(start, c))
start = c+1
}
if (char === encapsulator_char && (c === 0 || text[c-1] !== escape_char) )
encapsulated = ! encapsulated
}
fields.push(text.substring(start))
return fields
}
https://jsfiddle.net/7hty8Lvr/1/
const csvSplit = (line) => {
let splitLine = [];
var quotesplit = line.split('"');
var lastindex = quotesplit.length - 1;
// split evens removing outside quotes, push odds
quotesplit.forEach((val, index) => {
if (index % 2 === 0) {
var firstchar = (index == 0) ? 0 : 1;
var trimmed = (index == lastindex)
? val.substring(firstchar)
: val.slice(firstchar, -1);
trimmed.split(",").forEach(v => splitLine.push(v));
} else {
splitLine.push(val);
}
});
return splitLine;
}
this works as long as quotes always come on the outside of values that contain the commas that need to be excluded (i.e. a csv file).
if you have stuff like '1,2,4"2,6",8'
it will not work.
Assuming your string really looks like '[a, b, c, "d, e, f", g, h]', I believe this would be 'an acceptable use case for eval():
myString = 'var myArr ' + myString;
eval(myString);
console.log(myArr); // will now be an array of elements: a, b, c, "d, e, f", g, h
Edit: As Rocket pointed out, strict mode removes eval's ability to inject variables into the local scope, meaning you'd want to do this:
var myArr = eval(myString);
I've had similar issues with this, and I've found no good .net solution so went DIY. NOTE: This was also used to reply to
Splitting comma separated string, ignore commas in quotes, but allow strings with one double quotation
but seems more applicable here (but useful over there)
In my application I'm parsing a csv so my split credential is ",". this method I suppose only works for where you have a single char split argument.
So, I've written a function that ignores commas within double quotes. it does it by converting the input string into a character array and parsing char by char
public static string[] Splitter_IgnoreQuotes(string stringToSplit)
{
char[] CharsOfData = stringToSplit.ToCharArray();
//enter your expected array size here or alloc.
string[] dataArray = new string[37];
int arrayIndex = 0;
bool DoubleQuotesJustSeen = false;
foreach (char theChar in CharsOfData)
{
//did we just see double quotes, and no command? dont split then. you could make ',' a variable for your split parameters I'm working with a csv.
if ((theChar != ',' || DoubleQuotesJustSeen) && theChar != '"')
{
dataArray[arrayIndex] = dataArray[arrayIndex] + theChar;
}
else if (theChar == '"')
{
if (DoubleQuotesJustSeen)
{
DoubleQuotesJustSeen = false;
}
else
{
DoubleQuotesJustSeen = true;
}
}
else if (theChar == ',' && !DoubleQuotesJustSeen)
{
arrayIndex++;
}
}
return dataArray;
}
This function, to my application taste also ignores ("") in any input as these are unneeded and present in my input.
Given this input s1 = "dadxx" s2 = "ddxx" I'd expect the output to contain a bunch of a,b pairs wherever each character in s1 matched a character in s2 and vice versa (duplicates allowed). Among those pairs would be 0,0 because s1[0] and s2[0] are both equal to d.
The problem is that my output doesn't contain 2,1 even though s1[2] and s2[1] are both equal to d.
Can someone fix my algorithm or make a better one?
Here's a JSFiddle if it helps.
Here's my code:
// For each char, see if other string contains it
s1 = 'dadxx'
s2 = 'ddxx'
matchChars(s1,s2)
matchChars(s2,s1)
function matchChars(a,b) {
for (i = 0; i < a.length; i++) {
found = b.indexOf(a[i])
if (found >= 0) {
if (a===s1) console.log(i,found)
else console.log(found,i)
}
}
}
I believe the problem you're having is that you're only checking for a single match for s1[i] in s2 by using indexOf. That will find the first index of a matched value, not every index.
If you instead iterate through both strings and compare every character, you get the result I think you're trying to achieve.
// Define strings
s1 = 'dadxx'
s2 = 'ddxx'
matchChars(s1,s2)
matchChars(s2,s1)
function matchChars(a,b) {
// Convert strings to lower case for case insensitive matching
// Remove if case sensitive matching required
a = a.toLowerCase();
b = b.toLowerCase();
// Iterate through every letter in s1
for (i = 0; i < a.length; i++) {
// Iterate through every letter in s2
for (j = 0; j < b.length; j++) {
// Check if the letter in s1 matches letter in s2
if (a[i] === b[j]) {
// Changed per request of OP
(a === s1) ? console.log(i, j) : console.log(j, i);
// console.log([i, j]);
}
}
}
}
Working JSBin example: https://jsbin.com/wecijopohi/edit?js,console
You say duplicates are allowed but not required. I'm submitting this as a more modern approach, not as a correction to the accepted solution, which looks good to me. https://jsfiddle.net/avc705zr/3/
match = (a, b) => {
let re, match, matches = []
a.split('').forEach((l, i) => {
re = new RegExp(l, 'g')
while ((match = re.exec(b)) != null) {
matches.push([i, match.index])
}
})
return matches
}
However, in my experience when you actually need functionality like this, you only need one of the strings to exhausted. In other words, you are looking for matches in string 2 of all instances in string 1 -- which is to say, unique characters in string 1. So a modification which might come up in the real world might instead be like:
Array.prototype.unique = function() {
return this.filter(function (value, index, self) {
return self.indexOf(value) === index;
});
}
match = (a, b) => {
let re, match, matches = []
a.split('').unique().forEach(l => {
re = new RegExp(l, 'g')
while ((match = re.exec(b)) != null) {
matches.push([l, match.index])
}
})
return matches
}
I'm attempting to compare an original string argument with its reverse. In essence, this function is supposed to verify whether or not a given string is a palindrome. Key points:
String needs to be converted to all lowercase, which I did.
String needs to consist of only alphanumeric characters, which I did.
When compared, the original string and formatted string must match. If they do, the boolean value of true gets returned, otherwise false does.
Here is the source code: JS Fiddle | Alternatively, code is below:
function palindrome(str) {
var reverseString;
var temp;
var formatted;
// make sure input gets converted to lowercase
temp = str.toLowerCase();
// make sure all non-alphanumeric characters get removed
// once converted to lowercase, ensure that all special characters and digits are stripped from the string
formatted = temp.replace(/[^A-Za-z]/g, '');
// now we need to compare two strings: the raw input vs the string in reverse
for (i = formatted.length -1; i >= 0; i--) {
reverseString += formatted[i];
}
if (reverseString === str) {
return true;
}
return false;
}
palindrome("123$EYE");
function palindrome(str) {
var reverseString=""; // initialize every string to ""
var temp="";
var formatted="";
temp = str.toLowerCase();
formatted = temp.replace(/[^A-Za-z0-9]/g, ''); // I added 0-9 in your regex to have numbers in your string
for (i = formatted.length -1; i >= 0; i--) {
reverseString += formatted[i];
}
if (reverseString === formatted) { // change str to formatted
return true;
}
return false;
}
var isPal = palindrome("123$EYE");
alert(isPal); // try it on `alert` if it is true or false
Your code is ok. But you have some flaws. You should initialize your String to "" so it will not have a value of undefined. The one you put on your if statement is str which is your original String word, you should put your formatted String because that is the one you removed the special characters.
Why reverse and compare? You just need to compare the characters of the same position from the head and from the tail. First str[0] and str[length - 1], then str[1] and str[length - 2], and so on. Till you reach the middle, or any comparison fails.
function isPalindrome(str) {
var len = str.length
for (var i = 0; i < Math.ceil(len/2); i++) {
if (str[i] !== str[len - 1 - i]) {
// or add more comparison rules here
return false
}
}
return true
}
isPalindrome('1') // true
isPalindrome('121') // true
isPalindrome('1221') // true
isPalindrome('1211') // false
alphanumeric characters?
function palindrome(str) {
var temp;
temp = str.toLowerCase();
temp = temp.replace(/[^A-Za-z0-9]/g, '');
console.log(temp);
for (let a = 0, b = temp.length - 1; b > a; a++, b--) {
if (temp.charAt(a) !== temp.charAt(b))
return false;
}
return true;
}
You didn't initialize reverseString so it will be undefined at the beginning. Adding a character 'a' to undefined returns a string 'undefineda', instead of 'a' which you probably expect.
Change your code to
var reverseString = '';
and it'll work
Here is an elegant way to reverse the text:
var rev = temp.split('').reverse().join(''); // reverse
check out fiddle:
function palindrome(str)
{
var temp = str.toLowerCase() // converted to lowercase
.replace(/[^A-Za-z]/g, ''); // non-alphanumeric characters removed
var rev = temp.split('').reverse().join(''); // reverse
console.log(temp, ' === ', rev, ' is ', temp === rev);
if(temp === rev)
{
return true;
}
return false;
}
var out = palindrome("123$EYE");
document.getElementById('divOutput').innerHTML = out;
<div id="divOutput"></div>
What the challenge asks:
Using the JavaScript language, have the function LetterChanges(str) take the str parameter being passed and modify it using the following algorithm. Replace every letter in the string with the letter following it in the alphabet (ie. c becomes d, z becomes a). Then capitalize every vowel in this new string (a, e, i, o, u) and finally return this modified string.
My solution:
function LetterChanges(str) {
var alphabet = [a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z];
var vowels = [a,e,i,o,u];
var stringToArray = str.split("");
for (i=0; i<=stringToArray.length; i++){ //goes through new array one-by-one
var originalLetter = stringToArray[i] // names each letter
var alphabetPosition = alphabet.indexOf(); // finds letter position in alphabet array
var newAlphabetPosition = alphabetPosition + 1; // adds one to that position
var newLetter = alphabet[newAlphabetPosition]; // changes the old letter to the new
newLetter = stringToArray[i]; // sends new letter to its position on new array
if (newLetter.isInArray(vowels){ // finds if new letter is a vowel
newLetter = newLetter.toUpperCase(); // if yes, turn into upper case
}
str = stringToArray.toStr() //turns array back to string, and names it str
}
return str;
}
I've tried to be very clear on my thinking, adding the steps one by one. Please refrain from using quick methods, since I really want to correctly understand the reasoning behind the challenge, and not memorize methods.
The code doesn't work... because of a few errors:
What is i? Did you forget to declare it?
Once you convert a string to an array... the first character starts at 0, and the last character is length -1. Your for-loop conditional has i <= stringToArray.length which would include one character beyond the array length.
var alphabetPosition = alphabet.indexOf(); Index of what? Did you forget indexOf(originalLetter)?
You forgot "z". You need some logic to "wrap-around" back to "a".
isInArray isNotAFunctionYouShowedUs. Actually Javascript only has "indexOf" which returns -1 on no-match... unless I'm mistaken.
function LetterChanges(str) {
for (var i = 0; i < str.length; i++) {
var newCharCode = str.charCodeAt(i) + 1; //Get Decimal Value for character at index "i", and increment by 1.
if (newCharCode == 123) { //Pesky 'z' becomes '{'. Lets change it to 'a' instead.
newCharCode = 97; // 'a' = 97.
}
if ([97,101,105,111,117].indexOf(newCharCode)!=-1) { //Is it a vowel? (97 = a, 101 = e, 105 = i, 111= o, 117 = u)
newCharCode-=32; //Make it capital. (65 = A, 69 = E, 73 = I, 79 = O, 85 = U)
}
console.log(newCharCode);
str = str.substr(0,i) + String.fromCharCode(newCharCode) + str.substr(i+1); //Convert it back to a character, and stick it back into the string.
console.log(str);
}
return str;
}
I marked up something kinda quick... just for fun. (untested) It only makes use of 2 variables and does some old fashioned ascii trickery.
My CoderByte Solutions (https://github.com/ambatiramireddy/My-CoderByte-Solutions)
function LetterChanges(str) {
var vowels = 'aeiou', result = '', changedChar;
for (i = 0; i < str.length; i++) {
var c = str.charCodeAt(i);
if (c >= 97 && c < 122)
changedChar = String.fromCharCode(c + 1);
else if (c == 122)
changedChar = String.fromCharCode(97);
else
changedChar = str[i];
if (vowels.indexOf(changedChar) != -1)
changedChar = changedChar.toUpperCase();
result += changedChar;
}
return result;
}