I wanted to use two Not and one and in booleans to test if the variable is neither upper case nor lower case.
I used this code so far but it didn't work as required:
else if ((x[i]) !== (x[i].toUpperCase()) && (x[i]!== x[i].toLowerCase()) ){
x.splice(x[i], 1);
}
This code was for a function that sorts entered strings yet uppercase are sorted first.
Here is the full code, I am also open to understanding better ways to create this function apart from boolean logic and the array methods I used.
function alpha(str){ // United States
var x = str.split(""); // [U,n,i,t,e,d,S,t,a,t,e,s]
var cap = [];
var small = [];
for (var i = 0; i<x.length; i++){
if (x[i] == x[i].toUpperCase()){
cap.push(x[i]);
}
else if ((x[i]) !== (x[i].toUpperCase()) && (x[i]!== x[i].toUpperCase()) ) {
x.splice(x[i], 1);
}
else {small.push(x[i]);}
}
var z = cap.sort();
var y = small.sort();
return z.concat(y).join("");
}
Please note the second else if statement is only useful because the code adds an empty space string at the beginning of the output, I'm not sure where it comes from, so please let me know if you have any idea how to sort this even without using the second else if.
In the ASCII table, upper case letters come first. That's why they come first when you sort alphabetically. Here's a link to a page on Wikipedia that shows the table with the upper case letters appearing first and their numerical equivalents. It's even printable.
Also, I took the liberty of simplifying your code a little. Seems like .splice() was not necessary.
function alpha( str ) {
var x = str.split(""); // [U,n,i,t,e,d,S,t,a,t,e,s]
var cap = [];
var small = [];
var length = x.length;
for (var i = 0; i < length; i++) {
if (x[i] === x[i].toUpperCase()) {
cap.push(x[i]);
} else if (x[i] === x[i].toLowerCase()) {
small.push(x[i]);
}
}
return cap.sort().concat(small.sort()).join("");
}
Maybe explain what you're trying to do? It most likely has been done before in some form and you definitely came to the right place to find an answer.
Is this what you want to do?
var str = "United States";
function alpha(str) {
return str.split('').sort().join('');
}
alert(alpha(str));
In all programming languages (as far as i know), boolean expressions are always evaluated from the left to the right with brackets of course.
So in the following example my_func() is called first, and then if there is the chance that the complete expression becomes true my_other_func() is called
if (my_func() && my_other_func()) {
// I only get here if my_func() AND my_other_func() return true
// If my_func() returns false, my_other_func() is never called
}
The same is true for the "or" operator in the following example
if (my_func() || my_other_func()) {
// I only get here if my_func() OR my_other_func() return true
// If my_func() returns true, my_other_func() is not called
}
So back to your code, in details this part (I reformated it a bit for better readability):
if (x[i] == x[i].toUpperCase()){
// only uppercase here
cap.push(x[i]);
} else if (x[i] !== x[i].toUpperCase() && x[i] !== x[i].toUpperCase()) {
// tested twice the same thing, so Im really sure that its not uppercase :D
// only lowercase here
x.splice(x[i], 1);
} else {
// I will never reach this
small.push(x[i]);
}
Im not sure what you want to do, but I hope the comments help to understand your code.
Related
I want to implement the split method with a function
This is what i am trying to achieve
var string = 'aa,bb,c';
var separator = ',';
var stringList = string.split(separator);
function splitString() {
console.log(stringList);
}
This returns this array
["aa", "bb", "c"]
I am trying to implement the same with a function but it returns an empty array [] and not ["aa", "bb", "c"]
I have created a jsbin for who can help out.
function split(string,separator) {
var cache = [];
var cachInt = 0;
var lastWord = '';
for (var i = 0; i < string.length; i++) {
if(string[i] === separator) {
cachInt++
lastWord = ''
}
else {
lastWord = lastWord + string[i];
cache[cachInt] == lastWord;
}
}
return cache;
}
function splitString() {
console.log(split('string, separator',','));
}
You do this:
cache[cachInt] == lastWord;
Which should be, because you're not comparing, you're assigning:
cache[cachInt] = lastWord;
While we're at it, there is room for improvement. Your version has the line mentioned above. That line gets run every iteration of i. Thats not really needed, as you only want to perform a save on a split:
if(string[i] === separator) {
cache[cachInt] = lastWord; // Only assign when we find a seperator
cachInt++
lastWord = ''
} else {
lastWord = lastWord + string[i];
}
This has a tiny issue: The last part of string often doesn't have the seperator, it's a,b,c and not a,b,c,.
We can fix that easily with a check after the for to see if you have anything remaining:
if( lastWord!=='' ){
cache[cachInt] = lastWord;
}
return cache;
This has the added feature that it works as a rtrim() (wether you want that or not is up to you to fix).
Also, if you don't need to support older IE versions, then don't use var, use let. If you want to know why, this question explains it well.
Then, you're using a counter to remember which cachInt to use. As we now only use it once per "cacheInt", eg once per word, we know that each addition is +1, and only happens once per word. We also don't really care about the index, we just want each word to be added once. So, you can do cache[] = lastWord, or use push, which is slightly neater: cache.push(lastWord).
By removing the use for this counter, you can also remove the cachInt++ and the let/var cachInt at the beginning of the function, resulting in smaller code.
Result of all of the above:
https://jsbin.com/mejayuv/1/edit?html,js,console,output
Hey guys I am trying trying to right this javascript code into c++. I am doing quick sort and everything is straight forward minus the last step.
function quickSort(arr)
{
//base case if the arr is 1 or 0 then return the array
if(arr.length === 1 || arr.length === 0)
{
return arr;
}
var pivotIndex = Math.floor(arr.length/2);
var pivotValue = arr[pivotIndex];
var before = [];
var after = [];
for(var counter = 0; counter < arr.length; counter++)
{
if(counter === pivotIndex)
continue;
if(pivotValue <= arr[counter])
{
before.push(arr[counter])
}
else
{
after.push(arr[counter])
}
}
//this step I am having trouble rewriting in c++
return quickSort(after).concat(pivotValue).concat(quickSort(before));
}
I am having a hard time rewriting the recursive step in c++. I am not sure how concat 2 vector. I tried using the insert method but I keep getting an error about invalid use of void expression.
vector<int> quickSort(vector<int> arr)
{
if(arr.size() == 1 || arr.size() == 0)
{
return arr;
}
int pivotIndex = arr.size()/2;
int pivotValue = arr[pivotIndex];
vector<int> before;
vector<int> after;
//put values in before or after the piv
for(size_t counter = 0; counter < arr.size(); counter++)
{
if(counter == pivotIndex)
continue;
if(pivotValue <= arr[counter])
before.push_back( arr[counter]);
else
after.push_back( arr[counter]);
}
return //????? not sure how to do this
}
So, you realized that your core question was "how to concatenate two vectors", and you found a right answer: using insert. Now your question is about why you were getting "an error about invalid use of void expression." (That's the assumption my answer is for, at least.)
That's because you were likely trying to do something like the following:
return quickSort(after).insert( /* stuff */ );
which is wrong. In JavaScript, array.concat returns the concatenated array. It's return type is effectively Array, and so doing return arr.concat(arr2) returns an Array because arr.concat would return an Array. Further, in JavaScript, array.concat doesn't modify the array it was called on, but rather returns a new array.
In C++, however, vector.insert (#4 in the reference) returns void. That means it returns nothing. So when you try to return the result of insert, you get that error about invalid use of a void expression. Further, in C++, vector.insert does modify the vector it was called on.
So how do you use insert in this case?
vector<int> quickSort(vector<int> arr)
{
// ...
// Sort `before` and `after`
before = quickSort(before);
after = quickSort(after);
// Modify `after` and return it.
after.push_back(pivotValue);
after.insert(after.end(), before.begin(), before.end());
return after;
}
Note: My code isn't optimal and the idea of rewriting JS in C++ is also oddly specific. My answer is to simply outline the problem asked in the question, not to give a good C++ implementation of quick sort.
To concat two vector , you can use std::merge
like:std::merge(v1.begin(), v1.end(), v2.begin(), v2.end(), std::back_inserter(dst));
I am currently working on a challenge to convert any amount of arbitrary numbers entered into the function below as a currency (expressed by a string where every three characters are separated by a comma). All was okay until I realized that if the length of the number entered was 4, then the comma would need to be placed as 1,234 rather than 123,4.
It seems the function has spiralled out of control a little when I wrapped the initial if statement around my for loop. (1) I keep getting thrown an 'Uncaught SyntaxError: Unexpected token else' in the console. (2) I thought it may be due trying to place an if/else around the for/if/else. Any light shed on my error would be much appreciated. Charlie
function toCurrency(price){
var newStrng = price.toString().split("");
var stringCh = [];
if(newStrng.length===4){
console.log("gotcha");
stringCh = newStrng.splice(1,0,",");
return stringCh;
} else {
for(var i = 0; i < newStrng.length; i++) {
if(i %3 === 0 && i !== 0){
stringCh.push(",");
stringCh.push(newStrng[i]);
}
} else {
stringCh.push(newStrng[i]);
}
}
var finallyDone = stringCh.join("");
return finallyDone;
}//EO function
The if statement in the following block
for(var i = 0; i < newStrng.length; i++) {
if(i %3 === 0 && i !== 0){
stringCh.push(",");
stringCh.push(newStrng[i]);
}
} else {
stringCh.push(newStrng[i]);
}
}
has an extra }, right before the else. Take it out and you should no long receive the syntax error.
You can make it easier to spot mistakes like this in the future by ensuring your code is properly indented so you can see which brackets are associated with which blocks. Though I appreciate it could be reasonably indented in the source code and may not have copied across to SO perfectly.
There is a } in the wrong place inside the for loop, that need to be moved after the else block. As it is, the if statement is located in the for loop, but the else block is located outside of the loop, which is not valid syntax.
function toCurrency(price){
var newStrng = price.toString().split("");
var stringCh = [];
if(newStrng.length===4){
console.log("gotcha");
stringCh = newStrng.splice(1,0,",");
return stringCh;
} else {
for(var i = 0; i < newStrng.length; i++) {
if(i %3 === 0 && i !== 0){
stringCh.push(",");
stringCh.push(newStrng[i]);
} else {
stringCh.push(newStrng[i]);
}
}
}
var finallyDone = stringCh.join("");
return finallyDone;
}//EO function
remove } after,
stringCh.push(newStrng[i]);
I have found a few posts on here with similar questions but not entirely the same as what I am trying. I am currently using a simple if statement that checks the data the user enters then checks to see if it starts with a number of different values. I am doing this with the following:
var value = string;
var value = value.toLowerCase();
country = "NONE";
county = "NONE";
if (value.indexOf('ba1 ') == 0 || value.indexOf('ba2 ') == 0 || value.indexOf('ba3 ') == 0) { //CHECK AVON (MAINLAND UK) UK.AVON
country = "UK";
county = "UK.AVON";
} else if(value.indexOf('lu') == 0){//CHECK BEDFORDSHIRE (MAINLAND UK) UK.BEDS
country = "UK";
county = "UK.BEDS";
}
I have about 20-30 different if, else statements that are basically checking the post code entered and finding the county associated. However some of these if statements are incredibly long so I would like to store the values inside an array and then in the if statement simply check value.indexOf() for each of the array values.
So in the above example I would have an array as follows for the statement:
var avon = new Array('ba1 ','ba 2','ba3 ');
then inside the indexOf() use each value
Would this be possible with minimal script or am I going to need to make a function for this to work? I am ideally wanting to keep the array inside the if statement instead of querying for each array value.
You can use the some Array method (though you might need to shim it for legacy environments):
var value = string.toLowerCase(),
country = "NONE",
county = "NONE";
if (['ba1 ','ba 2','ba3 '].some(function(str) {
return value.slice(0, str.length) === str;
})) {
country = "UK";
county = "UK.AVON";
}
(using a more performant How to check if a string "StartsWith" another string? implementation also)
For an even shorter condition, you might also resort to regex (anchor and alternation):
if (/^ba(1 | 2|3 )/i.test(string)) { … }
No, it doesn’t exist, but you can make a function to do just that:
function containsAny(string, substrings) {
for(var i = 0; i < substrings.length; i++) {
if(string.indexOf(substrings[i]) !== -1) {
return true;
}
}
return false;
}
Alternatively, there’s a regular expression:
/ba[123] /.test(value)
My recomendation is to rethink your approach and use regular expressions instead of indexOf.
But if you really need it, you can use the following method:
function checkStart(value, acceptableStarts){
for (var i=0; i<acceptableStarts.length; i++) {
if (value.indexOf(acceptableStarts[i]) == 0) {
return true;
}
}
return false;
}
Your previous usage turns into:
if (checkStart(value, ['ba1', ba2 ', 'ba3'])) {
country = 'UK';
}
Even better you can generalize stuff, like this:
var countryPrefixes = {
'UK' : ['ba1','ba2 ', 'ba3'],
'FR' : ['fa2','fa2']
}
for (var key in countryPrefixes) {
if (checkStart(value, countryPrefixes[key]) {
country = key;
}
}
I'd forget using hard-coded logic for this, and just use data:
var countyMapping = {
'BA1': 'UK.AVON',
'BA2': 'UK.AVON',
'BA3': 'UK.AVON',
'LU': 'UK.BEDS',
...
};
Take successive characters off the right hand side of the postcode and do a trivial lookup in the table until you get a match. Four or so lines of code ought to do it:
function getCounty(str) {
while (str.length) {
var res = countyMapping[str];
if (res !== undefined) return res;
str = str.slice(0, -1);
}
}
I'd suggest normalising your strings first to ensure that the space between the two halves of the postcode is present and in the right place.
For extra bonus points, get the table out of a database so you don't have to modify your code when Scotland gets thrown out of leaves the UK ;-)
I've been writing a javascript function which returns true if the value matches one of about 4 values (just 3 in the example below). The problem is, when I have just two values the function works correctly, but adding a third breaks the code.
I'm pretty new to javascript and I'm guessing there's a much better way of doing this? I've tried searching but found nothing as of yet.
Any help is much appreciated.
function isValid(elem, helperMsg){
var sn6 = /[sS][nN]6/;
var sn5 = /[sS][nN]5/;
var sn38 = /[sS][nN]38/;
if(elem.value.match(sn6 || sn5 || sn38)){
//do stuff
return true;
}else{
return false;
}
}
Edit:
Here's my second attempt with an array:
function isLocal(elem, helperMsg){
var validPostcodes=new Array();
validPostcodes[0]= /[wW][rR]12/;
validPostcodes[1]= /[cC][vV]35/;
validPostcodes[2]= /[sS][nN]99/;
validPostcodes[3]= /[sS][nN]6/;
validPostcodes[4]= /[sS][nN]5/;
validPostcodes[5]= /[sS][nN]38/;
validPostcodes[6]= /[oO][xX]29/;
validPostcodes[7]= /[oO][xX]28/;
var i = 0;
for (i = 0; i < validPostcodes.length; ++i) {
if(elem.value.match(validPostcodes[i])){
// do stuff
return true;
}else{
alert(helperMsg);
elem.focus();
return false;
}
}
}
a || b || c
is an expression that evaluates to a boolean. That means that you're running either match(true) or match(false). You must write it as:
match(a) || match(b) || match(c)
Another option would be to store them in an array and loop over it. That would mean if the number of patterns grew you wouldn't have to change code other than the list of patterns. Another approach, though limited to this situation, might be to change the pattern to one that is equivalent to or-ing the three options together (untested, and I'm a bit rusty on regex):
elem.value.match(/[sSnN][6|5|38]/)
Array based example:
var patterns = [/../, /.../];
for (var i = 0; i < patterns.length; ++i) {
if (elem.value.match(patterns[i])) { return true; }
}
In real code, I would probably format it like this:
function isValid(elem, helperMsg){
var patterns = [/../, /.../],
i = 0;
for (i = 0; i < patterns.length; ++i) {
if (elem.value.match(patterns[i])) {
return true;
}
}
}
That's just a habit though since JavaScript hoists variables to the top of their scope. It's by no means required to declare the variables like that.