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;
Related
This is my first question, so excuse me if I mess something up. I'm new.
Anywho, recently I've been designing a function which takes a string and 2 substrings, and then returns an array of the positions of both substrings so I can later substring the actual string using the positions of the substrings I'm searching for. I hope that makes sense.
function m(s,s1,s2,prevTable){
var a = prevTable || []
if (s.indexOf(s1) > -1 && s.indexOf(s2, s.indexOf(s1)) > -1){
a.push([s.indexOf(s1),s.indexOf(s2, s.indexOf(s1))+s2.length])
s=s.substring(s.indexOf(s2, s.indexOf(s1)+s2.length))
console.log(s)
m(s,s1,s2,a);
}
return a;
}
So to summarize it makes an array (a), finds the position of s1 and s2 (plus it's own length so it includes s2) in the source string (s), adds them to the array as it's own array.
E.g a would be: a=[[2,5]], deletes up to where s2 was found (+s2.length to include s2), and then repeats it with the new string unless it can't find both s1 and s2, in which case it returns a.
However, it does not work as I intended it to.
Upon running this:
var s = "Hey. This is pointless. Middle is always neutral. This is not
pointless."
var a=m(s,"This","pointless.")
for (i=0;i<a.length;i++){
console.log(s.substring(a[i][0],a[i][1]))
}
The result I get is:
This is pointless.
dle is always neutral.
When I am expecting:
This is pointless.
This is not pointless.
Also, is there a name for this technique?
What you are trying to do could be accomplished more easily using regular expressions (MSDN Docs).
Here is a simple example, note: I threw this together quickly, it may not handle all input perfectly.
function splitBetweenTwoStrings(str, s1, s2){
var reg = new RegExp("("+s1+".*?"+s2+")", "g");
var result = [];
var r = null;
//get all instances and push into result array
while((r=reg.exec(str))){
result.push(r[1]);
}
return result;
}
console.log(splitBetweenTwoStrings("Hey. This is pointless. Middle is always neutral. This is not pointless.","This","pointless."))
You could do it by creating another method to check indices (I received help from (here)[https://stackoverflow.com/a/20968478/7535444]) and then loop over the occurrences.
var s = "Hey. This is pointless. Middle is always neutral. This is not pointless.";
var results = m(s, "This", "pointless.");
for (var i = 0; i < results.length; i++) {
console.log(results[i]);
}
function m(s, s1, s2) {
var s1Occurences = occurences(s, s1);
var s2Occurences = occurences(s, s2);
var loopCount = Math.min(s1Occurences.length, s2Occurences.length);
var results = [];
for (var i = 0; i < loopCount; i++) {
results.push(s.substring(s1Occurences[i], s2Occurences[i] + s2.length));
}
return results;
}
function occurences(main, sub) {
var indices = [];
for(var pos = main.indexOf(sub); pos !== -1; pos = s.indexOf(sub, pos + 1)) {
indices.push(pos);
}
return indices;
}
The problem with your code is, that in your example the second array element of "a" ([[5,23],[27,49]]) is relative to the temporary "s"-string created for the second call of m(). You would have to shift the values by the length of the cut-off-part of the "s"-string: [[5,23],[27+23,49+23]].
But I would recommend to use something like Will P.'s method.
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 have some file contents I'd like to pass on to my server using a javascript function. In the file, there are many empty lines, or those which contain useless text. So far I read every line in as a string stored in an array.
How do I then loop through that content skipping multiple lines such as lines 24,25, 36, 42, 125 etc. Can I put these element id's into an array and tell my for loop to run on every element except these?
Thanks
you can't tell your for loop to iterate all, but skip certain elements. it will basically just count in any direction (simplified) until a certain critera has been met.
you can however put an if inside your loop to check for certain conditions, and chose to do nothing, if the condition is met. e.g.:
(pseudo code below, beware of typing errors)
for(var line=0; line < fileContents.length; line++) {
if(isUselessLine(line)) {
continue;
}
// process that line
}
the continue keyword basically tells the for loop to "jump over" the rest of the current iteration and continue with the next value.
The isUselessLine function is something you'll have to implement yourself, in a way, that it returns true, if the line with the given linenumber is useless for you.
You can try this its not much elegent but will suerly do the trick
<html>
<body>
<p>A loop which will skip the step where i = 3,4,6,9.</p>
<p id="demo"></p>
<script>
var text = "";
var num = [3,4,6,9];
var i;
for (i = 0; i < 10; i++) {
var a = num.indexOf(i);
if (a>=0) {
continue;
}
text += "The number is " + i + "<br>";
}
document.getElementById("demo").innerHTML = text;
</script>
</body>
You could use something like this
var i = 0, len = array1.length;
for (; i < len; i++) {
if (i == 24 || i == 25) {
array1.splice(i, 1);
}
}
Or you can have an another array variable which got all the items that need to be removed from array1
Another method:
var lines = fileContents.match(/[^\r\n]+/g).filter(function(str,index,arr){
return !(str=="") && uselessLines.indexOf(index+1)<0;
});
If you have many indices to skip, and this depends on the elements of the array, you could write a function that returns the number of elements to skip over for each index in that array (or returns 1, if no skipping required):
for ( let i = 0;
i < array.length;
i += calcNumberOfIndicesToSkip( array, i )){
// do stuff to the elements that aren't
// automatically skipped
}
function calcNumberOfIndicesToSkip( array, i ){
// logic to determine number of elements to skip
// (this may be irregular)
return numberOfElementsToSkip ;
}
In your case:
// skip the next index (i+1)?
for ( let i=0; i<array.length; i+=skipThisIndex(i+1) ){
// do stuff
}
function skipThisIndex(i){
const indicesToSkip = [ 24, 25, 36, 42, 125 ];
return 1 + indicesToSkip.includes(i);
}
// returns 1 if i is not within indicesToSkip
// (there will be no skipping)
// => (equivalent to i++; normal iteration)
// or returns 1 + true (ie: 2) if i is in indicesToSkip
// => (index will be skipped)
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 am looping through an array of english phrases, and if i find a match, with the current text node, i replace it with it's translation in the non_english array. All of that works 100% for exact matches.
But for partial matches, I need to use the .match command, which allows for partial matches.
My code to search for exact matches is like this:
var found = $.inArray(value,en_lang);
Then if there is a found value, then do replacement of text. This method is fast and I love it.
However to do partial word/phrase matching, I have to use this looping code.
// loop thru language arrays
for (var x = en_count; x > 0; x--) {
// assign current from/to variables for replace
var from = en_lang[x];
var to = other_lang[x];
// if value match do translation
if (value.match(from)) {
content(node, value.replace(from, to));
}
// mark this node as translated
if ($.browser.msie == 'false') {
$(node).data('translated', 'yes');
}
}
This does the job but is pretty slow. After a lot of research, I have found that I can convert the english array to a list-based string via the join command.
But I am unable to come up with a function to search this list for a partial match, and return the position in the list.
I was trying out this old js function created in 2006. But I can't figure out how to get the position back, correctly.
function listfind(list, value, delimiters) {
if (!delimiters) {
var delimiters = ','
}
_TempListSplitArray = list.split(delimiters)
var FoundIdx = 0;
for (i = 0; i < _TempListSplitArray.length; i++) {
if (_TempListSplitArray[i] == value) {
FoundIdx = i + 1;
break
}
if (value.match(_TempListSplitArray[i])) {
FoundIdx = i + 1;
break
}
}
return FoundIdx
}
Thank you for your time.
Javascript has a foreach type of system but its still based on a loop
var array = ['hello', 'world'];
for(var key in array){
alert(array[key]);
}
Thats the best your getting for looping though an array but this way allso works with objects
var obj = {'one':'hello', 'two':'world'];
for(var key in obj){
alert("key: "+key+" value: "+obj[key]);
}
UPDATED for Comments on your question
You can just replace the text you know
var str = "hello World";
str = str.replace("hello", "Bye bye");
alert(str);