So I am doing a an exercise in which I have to sort a given string. Each word in the string contains a number in it(written like this 'H3llo'). The number that is in each word of the string should be placed in order according to the number in the new string that is to be returned.
For example if my input is "is2 Thi1s T4est 3a", then my function should return "Thi1s is2 3a T4est".
I almost cracked it but my output is incomplete. Here is my code:
function order(words) {
var lst = words.split(' ');
var count = 0;
var n = count + 1;
var s_n = n.toString();
var new_l = [];
while (count < lst.length) {
if (lst[count].includes(s_n) === true) {
new_l.push(lst[count])
}
count++
}
return new_l.join(' ');
}
When I test it, instead of getting:
console.log(order("is2 Thi1s T4est 3a"));
>>> 'Thi1s is2 3a T4est'
I get this:
console.log(order("is2 Thi1s T4est 3a"));
>>> 'Thi1s'
Can anyone explain to me what I am doing wrong?
You will basically need two loops - one for your current counter count i.e. the incremental number and another to iterate over the list of words to match that number. You increase the count only after you have finished iterating over the list.
function order(words) {
var lst = words.split(' ');
var count = 0;
var new_l = [];
while (count <= lst.length) {
for (i = 0; i < lst.length; i++) {
if (lst[i].includes(count)) {
new_l.push(lst[i])
}
}
count++;
}
return new_l.join(' ');
}
console.log(order("is2 Thi1s T4est 3a"));
Notice too that you don't need s_n -- the conversion is implicit, and you don't need === true as this is implicit in the if statement.
The main thing you are doing wrong is that you assign s_n to the string '1' before your loop, but you never update it within the loop. At the same time as you update count, you need to update s_n to the string of the next integer.
So you 'fixed' the part where you weren't updating the value of n or s_n within your outer loop, but the code still wont't work because you are now using count both to increment the digit you are looking for (within a word) and to increment the search through the list of words. You need an inner loop (and another variable) to increment the search.
Related
I'm trying to write a Javascript function that counts the vowels in a string by calling another function inside that function, but when I test it in the console it returns 0.
Here is my first function that works fine and recognizes if a string is a vowel:
function isVowel(ch){
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
};
For the second function none of my ideas have worked. Here are a few examples of what I have tried so far:
This one returns me a 0:
function countVowels(str){
var count = 0;
for(var i; i <= str.length; ++i){
if(isVowel(i)){
++count;
}
}
return count;
};
I also tried the above, but removing the .length after str in the for() area.
Another example, but this one gives me an error:
function countVowels(str){
var count = 0
var pattern = /[aeiouAEIOU]/
for(var i = 1; i <= str.length(pattern); ++i){
if(isVowel(i)){
++count;
}
}
return count;
};
I've tried various other functions as well, but for the sake of keeping this post relatively short I won't continue to post them. I'm quite new to Javascript and I'm not sure what I'm doing wrong. Any help would be greatly appreciated!
Try using .match() with the g attribute on your String.
g: global
i: case insensitive
Regexp documentation
function countVowels(ch){
return ch.match(/[aeiouy]/gi).length;
}
var str = "My string";
alert(countVowels(str)); // 2
Although Robiseb answer is the way to go, I want to let you know why you code is not working (I'm referring your first attempt). Basically you made two mistakes in the loop:
As CBroe stated, you are passing i to your isVowel function. i is a integer representing the index of the loop, not the actual character inside the string. To get the character you can do str.substr(i, 1), what means "give me one character from the position i inside the string".
You are not giving a initial value to the i variable. When you create a variable, it is undefined, so you can not increment it.
alert(countVowels("hello"));
function countVowels(str) {
var count = 0;
for (var i = 0; i <= str.length; ++i) {
if (isVowel(str.substr(i, 1))) {
count++;
}
}
return count;
};
function isVowel(ch) {
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
};
UPDATE: You will see that other answers use other methods to select the character inside the string from the index. You actually have a bunch of different options. Just for reference:
str.slice(i,i+1);
str.substring(i,i+1);
str.substr(i,1));
str.charAt(i);
str[i];
i is the index, not the character. It should be:
if (isVowel(str[i])) {
count++;
}
Also, str.length(pattern) is wrong. length is a property, not a function, so it should just be str.length.
You forgot to assign the value 0 to i variable
And parameter for isVowel is the character, not the index of string
Here information about the JS language: https://stackoverflow.com/tags/javascript/info
function isVowel(ch){
var pattern = /[aeiouAEIOU]/
return pattern.test(ch);
}
function countVowels(str){
var count = 0;
// you forgot to assign the value to i variable
for(var i = 0; i < str.length; i++){
// isVowel(str[i]), not isVowel(i)
if(isVowel(str[i])){
count++;
}
}
return count;
}
console.log(countVowels('forgot'))
Obviously you should do it this way:
function isVowel(c){
var lc = c.toLowerCase();
if(lc === 'y'){
return (Math.floor(Math.random() * 2) == 0);
}
return ['a','e','i','o','u'].indexOf(lc) > -1;
}
function countVowels(s){
var i = 0;
s.split('').each(function(c){
if(isVowel(c)){
i++;
}
});
return i;
}
console.log(countVowels("the quick brown fox jumps over the lazy dog"));
Which, although less efficient and less useful than other answers, at least has the entertaining property of returning a different count 50% of the time, because sometimes Y.
I'm just studying JS and I need to write a program that checkes if the string in the first element of the array contains all of the letters of the string in the second element of the array.
I've made a code like this:
function mutation(arr) {mutation: {
var lowerCaseStringOne = arr[0].toLowerCase();
var lowerCaseStringTwo = arr[1].toLowerCase();
if (lowerCaseStringOne === lowerCaseStringTwo) {
console.log(true);
break mutation;
}
var newArray = [];
for (var i = 0; i < lowerCaseStringTwo.length; i++){
console.log(lowerCaseStringTwo[i]);
if (lowerCaseStringTwo.indexOf(lowerCaseStringOne[i]) > 0) {
newArray.push(lowerCaseStringTwo[i]);
console.log('---');
}
}
var result = newArray.join("");
if (result === lowerCaseStringTwo) {
console.log(true);
} else {
console.log(false);
}
}
}
mutation(["Mary", "Aarmy"]);
I think it's very complicated, but I can't solve the problem - the "indexOf" function seems to ignore a second character in my loop - loggs it in the console but doesn't pushes into an array. I thought it could happen because first and second letters are similar, but it's not. No matter what letter, it just ignores it.
indexOf() will return 0 for the letter "a" in your example as the first instance is at position 0 in the array.
You should be using ">= 0"
I am trying to get all combination of a number. For example, input "123" should return ["123", "231", "213", "312", "321", "132"].
Here is my function:
function swapDigits(input) {
for (var i = 0; i++; i < input.length - 1) {
var output = [];
var inter = input.slice(i, i + 1);
var left = (input.slice(0, i) + input.slice(i + 1, input)).split("");
for (var j = 0; j++; j <= left.length) {
var result = left.splice(j, 0, inter).join("");
output.push(result);
}
}
console.log(output);
return output;
}
However this function returns undefined, could anyone tell me what's going wrong?
The errors with the for loop and scope have already been mentioned. Besides that, the splice method will change the string that it operates on. This means that the inner loop will never terminate because left keeps on growing, so j never reaches left.length.
If you are new to a language, I would suggest starting with an implementation that is close to the algorithm that you want to implement. Then, once you are comfortable with it, use more advanced language constructs.
See this fiddle for an example. This is the algorithm code:
function getPermutations(input)
{
if(input.length <= 1)
{
return [input];
}
var character = input[0];
var returnArray = [];
var subPermutes = getPermutations(input.slice(1));
debugOutput('Returned array: ' + subPermutes);
for(var subPermuteIndex = 0; subPermuteIndex < subPermutes.length; subPermuteIndex++ )
{
var subPermute = subPermutes[subPermuteIndex];
for(var charIndex = 0; charIndex <= subPermute.length; charIndex++)
{
var pre = subPermute.slice( 0, charIndex );
var post = subPermute.slice( charIndex );
returnArray.push(pre+character+post);
debugOutput(pre + '_' + character + '_' + post );
}
}
return returnArray;
}
Basically, this will walk to the end of the string and work its way back constructing all permutations of sub-strings. It is easiest to see this from the debug output for 1234. Note that 'Returned array' refers to the array that was created by the permutations of the sub-string. Also note that the current character is placed in every position in that array. The current character is shown between _ such as the 1 in 432_1_.
Returned array: 4
_3_4
4_3_
Returned array: 34,43
_2_34
3_2_4
34_2_
_2_43
4_2_3
43_2_
Returned array: 234,324,342,243,423,432
_1_234
2_1_34
23_1_4
234_1_
_1_324
3_1_24
32_1_4
324_1_
_1_342
3_1_42
34_1_2
342_1_
_1_243
2_1_43
24_1_3
243_1_
_1_423
4_1_23
42_1_3
423_1_
_1_432
4_1_32
43_1_2
432_1_
This algorithm doesn't enforce uniqueness. So, if you have a string 22 then you will get two results - 22,22. Also, this algorithm uses recursion which I think is quite intuitive in this case, however there are pure iterative implementations if you look for them.
There are several errors in that code.
You have the order of the parts of the for statement incorrect. The order is initialization, test, increment. So for (/* init */ ; /* test */ ; /* increment */)
You're creating a new array for each iteration of your outer loop.
I'm making this a CW because I haven't checked for further errors than the above.
I'm new to Java and I'm doing a uni course. I've been asked to design three functions.I have to find the difference between each adjacent numbers in an array, another to total the array and the last one to calculate the difference using the other functions then write a programme. I'm totally lost on the last function and my tutor has gone away on hols. Here is the code I have done so far. I don't want people doing the code for me but if anyone can advice me what I need to do I would appreciate your advice. I'm not sure how to loop the difference function into the array and store it into the new array I have made. If anyone could explain where I am going wrong I would love to hear from you!
var numberArray = [10,9,3,12];
// function difference will find the highest value of the two numbers,find the difference between them and return the value.
function difference(firstNumber, secondNumber)
{
if (firstNumber > secondNumber)
{
return (firstNumber - secondNumber);
}
else
{
return (secondNumber - firstNumber);
}
}
// function sum will add the total numbers in the array and return the sum of numbers.
function sum(numberArray)
{
numberTotal = 0
for (var total = 0; total < numberArray.length; total = total + 1)
{
numberTotal = numberTotal + numberArray[total]
}
{
return numberTotal
}
/*code the process that calculates a new array containing the differences between all the pairs
of adjacent numbers, using the difference() function you have already written.
This function should be named calculateDifferences() and should accept an array numberArray.
The function should first create a new empty array of the same size as numberArray
It should then calculate the differences between the pairs of adjacent numbers,
using the difference() function, and store them in the new array. Finally, the function should return the new array.
The calculation of the differences should be done in a loop, at each step finding the difference between each
array element and the next one along in the array, all except for the last difference,
which must be dealt with as a special case, because after the last element we have to wrap round to the start again.
So the final difference is between the last and first elements in the array.*/
function calculateDifferences()
var createArray = new Array (numberArray.length);
{
createArray = 0;
for (var c = 0; c < numberArray.length; c = c + 1)
{
createArray = difference(numberArray[c]);
}
{
return createArray
}
}
your implementation of function "calculateDifferences" is not correct.
this function should look like this:
function calculateDifferences()
{
var createArray = new Array (numberArray.length);
for (var c = 0; c < numberArray.length - 1 ; c = c + 1)
{
/*
because of the function "difference" has two parameters (firstNumber, secondNumber) in its declaration, we should give two arguments. (that are adjacent elements in array)
*/
createArray[c] = difference(numberArray[c],numberArray[c+1]);
}
/ *
calculating difference of first and last element of array and
assign it to returning array's last element.
*/
createArray[numberArray.length - 1] = difference(numberArray[0],numberArray[numberArray.length - 1]);
return createArray;
}
You should index createArray the same way you already do with numberArray[c].
I have written the following:
var pages=["[www.google.co.uk] This is the WWW. ","[www.yahoo.co.uk] This is also the WWW. "];
function findScoresC(s){
var scores=[];
var words=[];
var wordScore;
var indexScore=[];
s=s.toLowerCase();
for(i=0;i<pages.length; i++){
var lowerCaseContents=(pages[i].substring(pages[i].indexOf("]")+1,pages[i].lastIndexOf(" "))).toLowerCase();
words=lowerCaseContents.split(" ");
for(i=0;i<words.length;i++){
if(words[i].match(s)){
wordScore=1;
indexScore[i]=indexScore[i]+1};
scores[i] =indexScore[i]}};
return scores;
}
alert(findScoresC("w"));
The function aims to return an array ("scores") where each index of the array is the number of times the string s is found in each index of the "pages" array, excluding what is inside the square brackets - however, only finding the string s once within each word. So ideally, the first index of scores would be 1, because I have called the function with the letter w, and i would only like it to find the first w of "WWW" in the first index of pages - if this makes sense.
I have confused myself pretty epically in getting this far, so I have no idea why the function is returning ",,,," rather than numerical values for each index of scores - any ideas?
Thanks
When your for loop exits, i is equal to words.length, which is one greater than the last index of indexScore. You are assigning nothing at all to scores[i] each time through.
It might be because you have a nested for loop with the same index variable.
var pages=["[www.google.co.uk] This is the WWW. ","[www.yahoo.co.uk] This is also the WWW. ";
function findScoresC(s){
var scores=[];
var words=[];
s=s.toLowerCase();
for(i=0;i<pages.length; i++)
{
scores[i]=0;
var lowerCaseContents=(pages[i].substring(pages[i].indexOf("]")+1,pages[i].lastIndexOf(" "))).toLowerCase();
words=lowerCaseContents.split(" ");
for(j=0;j<words.length;j++)
{
if(words[j].match(s))
{
scores[i] += 1;
}
}
}
return scores;
}
alert(findScoresC("w"));
There were a few things. I replaced "i" with "j" for the inner index. You don't require a semicolon after a closing paren. You should have a semicolon after instructions (a couple were missing).
Probably the main issue (after the "i" issue) was that scores[i] should have been set outside the inner loop. This would have been clearer if the cosing parens had been separated out onto separate lines, instead of like "scores[i] =indexScore[i]}};".
It turned out that the variable indexScore was not required. That allowed me to bring scores[i] inside the inner loop to accumulate word hits directly.
Finally, I would prefer to communicate the pages variable to the function as an argument than to assume that it is available in the global space. I tend to avoid globals if I can.
var pages = [...];
function findScoresC(pages, s)
{
...
}
alert(findScoresC(pages, "w"));
Here's you're function fixed. It returns [1,1] which appears to be what you were going for. My notes are in the code.
var pages=["[www.google.co.uk] This is the WWW. ","[www.yahoo.co.uk] This is also the WWW. "];
function findScoresC(s){
var scores = [],
words = [],
wordScore;
// indexScore = [] <- this doesn't seem necessary
s = s.toLowerCase();
// Make sure to use `var i` and not just `i`; otherwise, you are creating a global variable.
for ( var i=0; i<pages.length; i++ ) {
// Initialize me!
scores.push(0);
var lowerCaseContents = pages[i].substring(
pages[i].indexOf("]") + 1, pages[i].lastIndexOf(" ")
).toLowerCase();
words = lowerCaseContents.split(" ");
// You were using `i` for this loop as well. No can do.
for ( var j=0; j<words.length; j++) {
if ( words[j].match(s) ) {
// wordScore = 1; <- I don't know what you're using this for
scores[i]++;
}
}
};
return scores;
}
console.log(findScoresC("w"));
here's a small function that counts how many times substring "subStr" occurs in "str", not counting [...]
function substrCount(str, subStr) {
var str = str.replace(/\[.+?\]/g, "");
var del = str.toLowerCase().split(subStr.toLowerCase()).join("");
return (str.length - del.length) / subStr.length;
}
the rest is obvious ;)
// edit: this is how you apply this function to an array
var someArray = ["whatever", "something", "else" ];
var counter = [];
for(var i = 0; i < someArray; i++)
counter[i] = substrCount(someArray[i], "something");
// or, to count only one match, i.e. just to test if a substring is present
counter[i] = substrCount(someArray[i], "something") > 0;