What is the problem in this simple js code? - javascript

I am wondering what`s the problem with this simple code. I am making a function where I need to get the length of the shortest word in a string. I know that I can find this function anywhere but,
why mine isn't working?
function findShort(s){
var arr = s.split(" ");
var out = 1000;
for (var i = 0; i < arr.length-1; i++){
if (arr[i] <= out){
out = arr[i].length;
}
}
return out;
}
The above function returns 1000 instead.

You need to compare the length of each word (arr[i].length), not each word itself (arr[i]) to the shortest length so far.
function findShort(s){
var arr = s.split(" ");
var out = 1000;
for (var i = 0; i < arr.length-1; i++){
if (arr[i].length <= out){ // <-- here!
out = arr[i].length;
}
}
return out;
}

Your problem is that when you compare strings in javascript, it doesn't use it's length. You have to use the "length" attribute of a String, like in the fixed code below. Also you have to save the result to give an output
function findShort(s){
var arr = s.split(" ");
var comp = 1000;
var out = "";
for (var i = 0; i < arr.length-1; i++){
if (arr[i].length <= comp){
comp = arr[i].length;
out = arr[i];
}
}
return out;
}
There still is a problem, if you want to have an array returned with all the shortest words (same length). You could add another if statement and make it add the word to an array when it's the same length, and clear it when there was found a shorter one.

Related

How to analyse complexity of an Algorithm that contains hidden loops made by external function or method?

First of all, I would like to apologize in case my title is not concise as it should be, but my point is, if you take a look at the following code which is selection sort algorithm, it's obvious for someone to analyze its complexity.
module.exports = function (arr) {
var temp;
for (var i = 0; i < arr.length; i++) {
var iTh = i;
for (var j = i+1; j < arr.length; j++) {
if (arr[j] < arr[iTh]) {
iTh = j;
}
}
temp = arr[i];
arr[i] = arr[iTh];
arr[iTh] = temp;
}
return arr;
}
But what if an algorithm contains hidden loops which are provided by particular language's functions or methods. For instance these two functions are both reversing a string, and they have JavaScript methods which have complexity behind them too.
So! How can someone analyze the complexity of these two and pick the optimal one? Or they don't qualify to be algorithms?
First Reverse
exports.reverse1 = function (str) {
if (str == undefined || str.length) {
return 0;
}
let collector = [];
for (var i = str.length; i >= 0; i--) {
collector.push(str.charAt(i));
}
return collector.join("");
}
Second Reverse
exports.reverse2 = function (str) {
if (str == undefined || str === "") {
return 0;
}
return str.split("").reverse().join("");
}

Need to filter out repeating consecutive characters in a string using JavaScript

It is one of the challenges in Codewars, and I am supposed to write a function that will take a string and return an array, in which I can't have two consecutive identical elements. Also, the order should not change.
For example, if I pass a string "hhhhheeeelllloooooohhheeeyyy", then the function should return an array = ["h","e","l","o","h","e","y"].
This is my code.
var uniqueInOrder=function(iterable){
//your code here - remember iterable can be a string or an array
var unique = [];
for( var i = 0; i < iterable.length; i++) {
unique.push(iterable[i]);
}
for( var j = 0, k = 1; j < unique.length; j++, k = j + 1 ){
if(unique[j] === unique[k]){
unique.splice(k,1);
}
}
return unique;
}
so, if I pass a string, such as "hhhhheeeeeellllloooo",it doesn't work as I intend it to because the value of j keeps incrementing, hence I can't filter out all the identical elements.
I tried tweaking the logic, such that whenever the unique[j] === unique[k] the value of j would become zero, and if that's not the case, then things would continue as they are supposed to do.
This got me an infinite loop.
I need your help.
The second for loop is fail because unique.length is not constant during the run.
I think your problem can be solved like this:
var temp = iterable[0];
unique.push(iterable[0]);
for( var i = 1; i < iterable.length; i++) {
if(iterable[i] != temp) {
unique.push(iterable[i]);
temp = iterable[i];
}
}
Hope it helps!
You only need to compare the current index of iterable against the last character in unique:
function(iterable){
var unique = []
for(var i=0; i< iterable.length; i++){
if(unique.length < 1){
unique.push(iterable[i])
} else if(iterable[i] !== unique[unique.length - 1]) {
unique.push(iterable[i])
}
}
return unique
}
I think this will help you:
var word="hhhhheeeelllloooooohhheeeyyy"
function doit(iterable){
var unique = []
unique[0]=iterable[0]
for(var i=1; i< iterable.length; i++){
if(iterable[i] !== unique[unique.length - 1]) {
unique.push(iterable[i])
}
}
return unique
}
alert(doit(word))
for loop will not fail because unique.length is dynamic, i.e will change with addition of new elements to array.
Tested in Internet Explorer too.
Here is the link to jsfiddle: https://jsfiddle.net/kannanore/z5gbee55/
var str = "hhhhheeeelllloooooohhheeeyyy";
var strLen = str.length;
var newStr = "";
for(var i=0; i < strLen; i++ ){
var chr$ = str.charAt(i);
//if(i==0) {newStr = chr$ };
if(chr$ == str.charAt(i+1)){
strLen = str.length;`enter code here`
}else{
newStr = newStr + chr$ ;
}
}
//document.write(newStr);
console.log(newStr);
//Answer: helohey

JavaScript trim character

I want to delete "()" from each value. How would I do that?
var arr = ["(one)","(two)","(three)","(four)","(five)"];
for(var i = 0; i < arr.length; i++){
console.log(arr[i]);
}
Since all the other answers are unnecessarily complicated, here's a simple one:
arr = arr.map(s => s.slice(1, -1));
You can do it in-place too if you prefer; the important part is .slice(1, -1), which takes a substring starting from the character at index 1 (the second character) and ending before the last character (-1).
String.prototype.slice documentation on MDN
var arr = ["(one)","(two)","(three)","(four)","(five)"];
for(var i = 0; i < arr.length; i++){
var arrLength = arr[i].length -2;
var shortArr = arr[i].substr(1,arrLength);
console.log(shortArr);
}
This gets one character less on the front and back
use replace
var arr = ["(one)","(two)","(three)","(four)","(five)"];
for(var i = 0; i < arr.length; i++){
var x = arr[i];
x = x.replace(/[()]/g,"");
console.log(x);
}
note:
i dedited, because alexander was right
so u need to use regex, "g" for search globally,
"[" "]" to find all character inside
This is fast and should work no matter how many parenthesis are in the string, it will remove them all.
arr[i] = arr[i].split(/\(|\)/g).join("");
This matches ( followed by anything that isn't ) followed by ). Would also fail for "(test(ing)123)", (if you care)
var arr = ["(one)","(two)","(three)","(four)","(five)"];
for(var i = 0; i < arr.length; i++) {
arr[i] = arr[i].replace(/\(([^)]+)\)/g, "$1");
}
This is much more simple/faster (but arguably more brittle):
var arr = ["(one)","(two)","(three)","(four)","(five)"];
for(var i = 0; i < arr.length; i++) {
arr[i] = arr[i].substr(1, arr[i].length - 2);
}

How to make a function that makes an array?

I am trying to make a function that generates an array of numbers within a certain range.
A very basic question but I couldn't find an explanation...
I tried this
var newArray = [];
function makeArrey(start, last) {
var length = last - start;
for(var i = 0; i <= length; i++) {
newArray[i] = start + i;
}
return newArray;
}
makeArrey(1, 100);
alert(newArray[4]); //4 is a random number to see if it works, it dont work
Your code is working perfectly fine. You're just forgetting that arrays start at index 0. So when you do something like newArray[4] it returns the 5th element of the array, which is 5 in your case.
For the sake of fixing your code so that it behaves nicer, do this:
function makeArray(start, last) {
var range = [];
var length = last - start;
for(var i = 0; i <= length; i++) {
range[i] = start + i;
}
return range;
}
var newArray = makeArray(1, 100);

undefined is returned in JavaScript function

When I call this function, sending for example: abc as the parameter,
the function returns: undefinedcba. I can't figure out why it's adding
'undefined' to my returned value. I'm probably overlooking something obvious
but I can't spot it. Thank you.
function FirstReverse(str) {
var str_arr1 = new Array();
var ans = '';
for(i=0; i < str.length; i++) {
str_arr1.push(str.charAt(i));
}
for(j=str.length; j >= 0; j--) {
ans += str_arr1[j];
}
return ans;
}
Strings are 0-indexed. str[str.length] does not exist.
j needs to start at str.length - 1.
Or, just return str_arr1.join();
The index of the string starts at 0, so string.length is always one number bigger than index of the last character in the string.
In the second for loop, use
for(var j=str.length -1; j >= 0; j--) {
The error is in the second for statement. See the solution:
function FirstReverse(str) {
var str_arr1 = new Array();
var ans = '';
for(i=0; i < str.length; i++) {
str_arr1.push(str.charAt(i));
}
for(j=str.length-1; j >= 0; j--) {
ans += str_arr1[j];
}
return ans;
}
Because when you pass 'abc' there are only 3 characters in it.
So arrray str_arr have elements at index 0, 1 and 2.
But you are looping for str.length i.e. for 3 times and str_arr[3] is not defined.
You should do this,
function FirstReverse(str) {
var str_arr1 = new Array();
var ans = '';
for(i=0; i < str.length; i++) {
str_arr1.push(str.charAt(i));
}
for(j=str.length-1; j >= 0; j--) {
ans += str_arr1[j];
}
return ans;
}
Looks like you want to reverse a string, which you can do in this javascript one liner
function reverse(s){
return s.split("").reverse().join("");
}
The reason you are getting an undefined is because your j starts with str.length, whereas it should be str.length-1. str_arr1[str.length] is out of bounds and therefore will be undefined.

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