I need to implement the .split method in my own way without using prebuilt functions. The method should receive a string divided into 2 sentences by a dot and divide them through a separator.
For example, there is this string:
'word wooord wooooooooord wooooooord. wooooooooord woooooord woooord wooooooooord', separator in this case: '. '
The result should be:
['word wooord wooooooooord wooooooord", "wooooooooord woooooord woooord wooooooooord']
I tried to implement it myself, the first problem I encountered is that the words from the string are added character by character to the new array. The second problem is that the output is still a string even though I declared an array earlier.
function split(str, splitter){
let arrSent = []
for (let i = 0; i < str.length; i++){
if (str[i] != splitter){
arrSent += str[i]
}
}
return arrSent
}
console.log(split('word wooord wooooooooord wooooooord. wooooooooord woooooord woooord wooooooooord', '. '))
Since the delimiter can have more than one character, you need a system to upfront collect a sample of characters (of the same length as the delimiter) to be then compared with the delimiter:
const split = (str, delimiter) => {
// If delimiter is empty string just return an array of characters
if (delimiter === "") return [...str];
const len = delimiter.length;
const iter = str.length - len + 1; // max needed iterations
const arr = [""]; // Prefill it with empty string
let idx = 0; // arr insertion pointer
for (let i = 0; i < iter; i++) {
// Collect len chars from str as a sample
// to compare with the delimiter:
let sample = "";
for (let x = i; x < i + len; x++) {
sample += str[x];
}
const isSplit = sample === delimiter;
const isEnded = i === iter - 1;
if (isSplit) {
i += len - 1; // Consume splitted characters
idx += 1; // Increment arr pointer
arr[idx] = ""; // Prepare the new array key as empty string
} else {
// If loop ended append the entire sample.
// Otherwise, append a single character:
arr[idx] += isEnded ? sample : str[i];
}
}
return arr
}
console.log(split("word. etc", ". "));
console.log(split("word. etc. ", ". "));
console.log(split(". word yep. . etc. ", ". "));
console.log(split("word", ". "));
console.log(split("word", "word"));
console.log(split("word", ""));
console.log(split("", ""));
above, idx (starting at 0) is used as the output's arr insertion pointer. The idx is incremented if the sample matches the delimiter. Also, if there's a match, we need to skip iterations i += len, to not include the delimiter in the output array.
To test, create many examples and right before return arr; use console.log(JSON.stringify(arr) === JSON.stringify(str.split(delimiter))); - it should return true for all the submitted tests.
Related
This
I'm able to return T!d!y. But i need T!d?y. I'm new to JS and I cant figure it out =(
function change(str) {
newString = str.split("");
for (let i = 1; i < newString.length - 1; i+=2) {
newString[i] = "!";
//newString[i] = "?";
}
return(newString.join("")); }
console.log(change("Teddy")); should return T!d?y
Use modulo to check whether the i being iterated over is one of the 3-7-11 sequence or the 1-5-9 sequence - then you can determine which character to insert.
function change(str) {
const arr = str.split("");
for (let i = 1; i < arr.length - 1; i += 2) {
arr[i] = i - 1 % 4 === 0
? "!"
: "?";
}
return arr.join("");
}
console.log(change("Teddy"));
Also remember
Declare your variables - doing newString = without a const (or something) before it implicitly creates a global variable, which is very often not what you want
.split returns an array; newString is not an accurate description of what the variable contains (perhaps instead call it arr or newArray or characters, or something like that)
You can add a check and update variable to be replaced.
Few pointers:
When looping, you will have to loop till last character. i < arr.length - 1 will cause issues for certain scenarios.
function change(str) {
const possibilities = [ "!", "?", "*" ];
let index = 0;
let newString = str.split("");
for (let i = 1; i < newString.length ; i += 2) {
newString[i] = possibilities[index % possibilities.length];
index++
}
return (newString.join(""));
}
console.log(change("Teddy"));
console.log(change("Javascript"));
I want to write a function which takes a sentence as an input and output a sorted sentence, and there are two criterias:
Each character of the word should be arranged in alphabetical order.
Words should be arranged in ascending order depending on its character count.
Note: - Word only can have lowercase letters
Example :
Inputs str = "she lives with him in a small apartment"
Output = "a in ehs him hitw eilsv allms aaemnprtt"
Here is my code.
function makeAlphabetSentenceSort(str) {
if (!str || str.length === 0) return 0;
var word = str.split(' ');
for (var j = 0; j < word.length; j++) {
word[j] = word[j].split('').sort().join('');
}
for (var h = 0; h < word.length - 1; h++) {
for (var i = 0; i < word.length - h - 1; i++) {
if (String(word[i]).length > String(word[i + 1]).length) {
var temp = word[i];
word[i] = word[i + 1];
word[i + 1] = temp;
}
}
}
return word.join(' ');
}
makeAlphabetSentenceSort("she lives with him in a small apartment");
Based on the assumption that the output should contain only lowercase letters.
Well if you want to use the built-in functions you could also write that as:
function makeAlphabetSentenceSort(str) {
if (!str) return str;
const nonCharacters = /[^a-z]/g; // to replace any thing other than letters
// We split the sentence to words by any whitespace first
return str.toLowerCase().split(/\s+/).map(word => {
// Here we remove all non-characters from the word
// And sort the remaining characters alphabetically
return word.replace(nonCharacters, '').split('').sort().join('');
// It might be that the sentence looks like:
// "Hey! ???"
// In that case the "word" ??? would become just an empty string
// since all the non-characters have been removed.
// But then you would end up with a result:
// " ehy"
// because the empty word would still get added to the beginning of the sentence
// Because of that we need to filter the empty words out
// And to do that I use this lil trick of mine, using "Boolean"
// as a filter function since Boolean('') is false
// and Boolean('any word') is true
}).filter(Boolean).sort((a, b) => {
// Here we sort all the words by their length
return a.length - b.length;
}).join(' ');
}
console.log(makeAlphabetSentenceSort("Isn't it?"));
console.log(makeAlphabetSentenceSort("she lives with him in a small apartment"));
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 beginner in JS. I've tried to understand Caesar Cipher ROT13, but it was too complicated for me. So I've tried to write my own code. Here it is below:
function encrip() {
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 str = "Ni Hao";
var string = str.toUpperCase();
for (var i = 0; i < string.length; i++) {
for (var k = 0; k < alphabet.length; k++) {
if(string.charAt(i) == alphabet[k]) {
/* console.log(string.charAt(i) + ' ' + alphabet.indexOf(alphabet[k])); */
}
}
}
}
encrip();
But I am stuck. How to do:
1. Get value from var str and then access to var alphabet , after change each letter from var str value to next 3 from alphabet (var str each element's current position would be changed) For example: Input: Ni Hao ==> output: QL KDR
2. Create universal code, I mean, not only for changing position by 3, but when I give value '5', each element would be changed by next 5 positions from alphabet. So output can be changed when I change its' value
I hope I explained everything clearly. Thanks everyone in advance for help!!
you can use the following function to encrypt english words, the 1st parameter is the string to encrypt and the 2nd for shifting
function encryp(str,pos){
var alpha="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var strUC=str.toUpperCase();
var enc="";
for(var i=0;i<strUC.length;i++){
if(strUC.charAt(i)!=" "){
enc+=alpha.charAt((alpha.indexOf(strUC.charAt(i))+pos)%26)
}
else{
enc+=" "
}
// in your case pos=3
}
return enc;
}
console.log(encryp("NiHao",3));
You don't need two for loops to do this. Iterate over the input string and find the index of each character in the alphabet array, if found add the shift to it to get the encrypted character.
To handle overflow use the modulus operator to cycle through the array.
Also I assume that you are not going use any special symbols to do the encryption.
function encrip(string, shift) {
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"];
string = string.toUpperCase();
let arr = [];
for (var i = 0; i < string.length; i++) {
let char = alphabet.indexOf(string[i]) !== -1 ? alphabet[(alphabet.indexOf(string[i]) %26) + shift] : " ";
arr.push(char);
}
let encryp = arr.join("");
console.log(encryp);
return encryp;
}
encrip("Ni Hao", 3);
First of all, instead of your inner for loop scanning the whole alphabet array, you can use the built-in function indexOf:
alphabet.indexOf('K') // returns 10
Secondly, you'll want to build up your enciphered string in a separate variable. For each letter, get the index of that letter in the alphabet, add your cipher offset parameter to that index and add the resulting letter from the alphabet to your new string. An important step is that when you add to the index of the letter, you want to make sure the resulting index is within range for the alphabet array. You can do that using the % (modulo) operator, which will wrap high values back round to the start of the array. In full:
function encipher(input, offset) {
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 str = input.toUpperCase();
var result = '';
for (var i = 0; i < str.length; i++) {
letterIndex = alphabet.indexOf(str.charAt(i));
if (letterIndex === -1) {
result += str[i]; // if the letter isn't found in the alphabet, add it to the result unchanged
continue;
}
cipheredIndex = (letterIndex + offset) % alphabet.length; // wrap index to length of alphabet
result += alphabet[cipheredIndex];
}
console.log(result);
}
encipher('Ni Hao', 5); // output: 'SN MFT'
$('.creditCardText').keyup(function() {
var foo = $(this).val().split("-").join(""); // remove hyphens
if (foo.length > 0) {
foo = foo.match(new RegExp('.{1,4}', 'g')).join("-");
}
$(this).val(foo);
});
I found this tutorial on putting dash after every 4 character from here my question is what if the character interval is not constant like in this example it is only after every 4 what if the interval is 3 characters "-" 2 characters "-" 4 characters "-" 3 characters "-" so it would appear like this 123-12-1234-123-123.
In this case, it is more convenient to just write normal code to solve the problem:
function format(input, format, sep) {
var output = "";
var idx = 0;
for (var i = 0; i < format.length && idx < input.length; i++) {
output += input.substr(idx, format[i]);
if (idx + format[i] < input.length) output += sep;
idx += format[i];
}
output += input.substr(idx);
return output;
}
Sample usage:
function format(input, format, sep) {
var output = "";
var idx = 0;
for (var i = 0; i < format.length && idx < input.length; i++) {
output += input.substr(idx, format[i]);
if (idx + format[i] < input.length) output += sep;
idx += format[i];
}
output += input.substr(idx);
return output;
}
$('.creditCardText').keyup(function() {
var foo = $(this).val().replace(/-/g, ""); // remove hyphens
// You may want to remove all non-digits here
// var foo = $(this).val().replace(/\D/g, "");
if (foo.length > 0) {
foo = format(foo, [3, 2, 4, 3, 3], "-");
}
$(this).val(foo);
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input class="creditCardText" />
While it is possible to do partial matching and capturing with regex, the replacement has to be done with a replacement function. In the replacment function, we need to determine how many capturing group actually captures some text. Since there is no clean solution with regex, I write a more general function as shown above.
You can split it using a regular expression. In this case, I'm using a expression to check for non-spaces with interval 3-2-4-3.
The RegExp.exec will return with a "match" array, with the first element containing the actual string. After removing the first element of the match, you can then join them up with dashes.
var mystring = "123121234123"
var myRegexp = /^([^\s]{3})([^\s]{2})([^\s]{4})([^\s]{3})$/g
var match = myRegexp.exec(mystring);
if (match)
{
match.shift();
mystring = match.join("-")
console.log(mystring)
}
Per further comments, the op clarified they need a fixed interval for when to insert dashes. In that case, there are several ways to implement it; I think regular expression would probably be the worst, in other words, overkill and overly complication solution.
Some simpler options would be to create a new character array, and in a loop append character by character, adding a dash too every time you get to the index you want. This would probably be the easiest to write and grok after the fact, but a little more verbose.
Or you could convert to a character array and use an 'insert into array at index'-type function like splice() (see Insert Item into Array at a Specific Index or Inserting string at position x of another string for some examples).
Pass the input value and the indexes to append the separator, first, it will remove the existing separators then just append separators on positions indexes.
export function addSeparators(
input: string,
positions: number[],
separator: string
): string {
const inputValue = input.replace(/-/g, '').split(''); // remove existing separators and split characters into array
for (let i = 0; i < inputValue.length; i++) {
if (positions.includes(i)) inputValue.splice(i, 0, separator);
}
return inputValue.join('');
}