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js Split array add space between words (not first)

I have a string Topic: Computer Science
And want to strip out topic: (but in fact I want this to work with any header on the string line) and return Computer Science.
I thought about splitting the components and then adding the spaces back in:
var subjectLine = thisLine.split(" ");
var subjectString = "";
for (i = 1; i < subjectLine.length; i++) {
subjectString += subjectLine[i] + " ";
}
But then I need to remove the last space from the string.
For each doesn't work as I need to NOT have the first element appended.
I'm not sure how to do this in js so it is reusable for many different lines and topic names that can come from the subjectLine

After splitting the line, remove the first element from the array, then join the rest back together.
var thisLine = "Topic: Computer Science";
var subjectLine = thisLine.split(" ");
subjectLine.splice(0, 1);
var subjectString = subjectLine.join(" ");
console.log(subjectString);

You might consider using a regular expression, it'll probably be a lot easier than working with arrays: match the non-space characters at the beginning of the string, followed by at least one space, and .replace with the empty string:
const subjectString = thisLine.replace(/^\S+\s+/, '');
const transform = line => line.replace(/^\S+\s+/, '');
console.log(transform('Topic: Computer Science'));

You need to know where the heading stops and the real data starts. Then delete all characters up to that point.
So, for instance, if you know that the heading ends with a colon, then do:
var line = "this is the topic: Computer Science";
var topic = line.replace(/^.*:\s*/, "");
console.log(topic);

Javascript regex match and get values from string

I've got a string of text which can have specific tags in it.
Example: var string = '<pause 4>This is a line of text.</pause><pause 7>This is the next part of the text.</pause>';
What I'm trying to do is do a regex match against the <pause #></pause> tag.
For each tags found, in this case it's <pause 4></pause> and <pause 7></pause>. What I want is to grab the value 4 and 7, and the string length divided by for the string in between the <pause #>...</pause> tags.
What I have for now is not much.
But I cant figure out how to grab all the cases, then loop through each one and grab the values I'm looking for.
My function for this looks like this for now, it's not much:
/**
* checkTags(string)
* Just check for tags, and add them
* to the proper arrays for drawing later on
* #return string
*/
function checkTags(string) {
// Regular expresions we will use
var regex = {
pause: /<pause (.*?)>(.*?)<\/pause>/g
}
var matchedPauses = string.match(regex.pause);
// For each match
// Grab the pause seconds <pause SECONDS>
// Grab the length of the string divided by 2 "string.length/2" between the <pause></pause> tags
// Push the values to "pauses" [seconds, string.length/2]
// Remove the tags from the original string variable
return string;
}
If anyone can explain my how I could do this I would be very thankful! :)

match(/.../g) doesn't save subgroups, you're going to need exec or replace to do that. Here's an example of a replace-based helper function to get all matches:
function matchAll(re, str) {
var matches = [];
str.replace(re, function() {
matches.push([...arguments]);
});
return matches;
}
var string = '<pause 4>This is a line of text.</pause><pause 7>This is the next part of the text.</pause>';
var re = /<pause (\d+)>(.+?)<\/pause>/g;
console.log(matchAll(re, string))
Since you're removing tags anyways, you can also use replace directly.

You need to make a loop to find all matched groups of your RegExp pattern in the text.
The matched group is an array containing the original text, the matched value and the match text.
var str = '<pause 4>This is a line of text.</pause><pause 7>This is the next part of the text.</pause>';
function checkTags(str) {
// Regular expresions we will use
var regex = {
pause: /<pause (.*?)>(.*?)\<\/pause>/g
}
var matches = [];
while(matchedPauses = regex.pause.exec(str)) {
matches.push([matchedPauses[1], matchedPauses[2].length /2]);
};
return matches;
}
console.log(checkTags(str));

As a start point since you have not much so far you could try this one
/<pause [0-9]+>.*<\/pause>/g
Than to get the number out there you match again using
/[0-9]+>/g
To get rid of the last sign >
str = str.slice(0, -1);

having an issue w/ .split in a JavaScript function that gets the max # of repeating chars per word in a string

I'm writing a JavaScript function that has to take in a string argument & determine the word or words with the maximum number or repeated (or most frequent) non sequential characters and return that word or words.
The way that I went about solving this problem was to first find the maximum number of times a character was repeated per word and record that number to use later in a function to test against every word in the string (or the array of strings as I later split it); if the word met the conditions, it's pushed into an array that I return.
My maxCount function seemed to work fine on its own but when I try to make it work together with my other function to get the words with max repeated chars returned, it's not working in JS Fiddle - it keeps telling me that "string.split is not a function" - I'll admit that the way I'm using it (string.split(string[i]).length) to analyze words in the string letter by letter is a bit unconventional - I hope there's some way to salvage some of my logic to make this work in the functions that can work together to get the results that I want.
Also, I don't know if I'm using Math.max correctly/in a "legal" way, I hope so. I've tried switching my variable name to "string" thinking that would make a difference but it did not even though my arguments are of the string variety and it's a string that's being represented.
Here's a link to my Fiddle:
https://jsfiddle.net/Tamara6666/rdwxqoh6/
Here's my code:
var maxCount = function (word) {
/// var maxRepeats = 0;
var numArray = [];
var string = word;
for (var i = 0, len = string.length; i < len; i++) {
//split the word('string') into letters at the index of i
numArray.push((string.split(string[i]).length) -1);
}
var max = Math.max(...numArray);
return max;
}
///console.log(maxCount("xxxxxxxxxxxxx"));
var LetterCount = function(string){
var repeatedChars = 0;
var wordArray=[];
var stringArray = string.split(" ");
for (var i = 0; i < stringArray.length; i++){
var eachWord = stringArray[i];
var maxRepeats = maxCount(stringArray);
if (repeatedChars < maxRepeats) {
repeatedChars = maxRepeats;
wordArray = [eachWord];
}else if (repeatedChars == maxRepeats) {
wordArray.push(eachWord);
}
}
return wordArray;
};
console.log(LetterCount("I attribute my success to cats"));
//should return ["attribute", "success"]
*** I've tried to map this first function onto the array formed when I split my string at the spaces but it is just returned me an empty array (I also might not have been using map correctly in this example); I also have tried using valueOf to extract the primitive value out of the array from the first function which also didn't work. I'm not really sure what to do at this point or what angle to take- I feel if I understood more what was going wrong I could more easily go about fixing it. Any help would be much appreciated. Thanks!

You are passing an array to maxCount at line 20, while it expects a string:
var maxRepeats = maxCount(stringArray);
You should use:
var maxRepeats = maxCount(eachWord);

If you are getting split is not a function error then first make sure that your string isn't null by printing it on console. If it isn't null then confirm that its a string not an array or some other thing.

How to remove all text except one with starts with some word?

im trying to remove all text except one in javascript
the idea is do something like
//jQuery("someelement").attr("class");
var classes= "cnode_1 timestamp_1413504000 item";
classes = classes.replace(/^(?!timestamp_)/,'');
i want to take only the text who starts with timestamp_, the expected ouput is :
timestamp_1413504000
i want this , then to grab the number
//now "classes" show be timestamp_1413504000
classes = classes.replace("timestamp_","");
the expected ouput is :
1413504000
i want to avoid use something like, split the clasess base on space, then use for bucle, and finally compare with indexOf

Do you need the "timestamp_" for something?
Why not just
= classes.replace(/^.*timestamp_(\d+).*/img, "$1");

Just use .match to get the part you want.
var classes= "cnode_1 timestamp_1413504000 item";
// match will return the matched string and the groups in an array
var ts = classes.match(/timestamp_(\d+)/)[1]; // match[1] is the group (\d+)
// 1413504000

I know you said that you want to avoid splitting or using indexOf, but javaScript doesn't have a 'startsWith' function. Why do you want to avoid doing that? Is the following unacceptable?
var NumberOutput;
var classList = document.getElementById('elementYouAreLookgingAt').className.split(/\s+/);
for (var i = 0; i < classList.length; i++) {
if (classList[i].indexOf("someClass") == 0) {
NumberOutput = classList[i].replace("someClass", "");
}
}

Split in to Sentences and Wrap With Tags

I'm trying to build a text fixing page for normalising text written in all capital letters, all lower case or an ungrammatical mixture of both.
What I'm currently trying to do is write a regular expression to find all full stops, question marks and line breaks, then split the string in to various strings containing all of the words up to and including each full stop.
Then I'm going to wrap them with <span> tags and use CSS :first-letter and text-transform:capitalize; to capitalise the first letter of each sentence.
The last stage will be writing a dictionary function to find user-specified words for capitalisation.
This question only concerns the part about writing a regex and splitting in to strings.
I've tried too many methods to post here, with varying results, but here's my current attempt:
for(var i=0; i < DoIt.length; i++){
DoIt[i].onclick = function(){
var offendingtext = input.value.toString();
var keeplinebreaks = offendingtext.replace(/\r?\n/g, '<br />');
var smalltext = keeplinebreaks.toLowerCase();
//split at each character I specify
var breakitup = smalltext.split(/[/.?\r\n]/g);
breakitup.forEach(function(i){
var i;
console.log(i);
var packagedtogo = document.createElement('span');
packagedtogo.className = 'sentence';
packagedtogo.innerHTML = breakitup[i];
output.appendChild(packagedtogo);
i++;
});
}
}
It was splitting at the right places before, but it was printing undefined in the output area between the tags. I've been at this for days, please could someone give me a hand.
How can I split a string in to multiple string sentences, and then wrap each string with html tags?

Your regex for the split is fine. Just forgot to escape a few characters:
var str = "SDFDSFDSF?sdf dsf sdfdsf. sdfdsfsdfdsfdsfdsfdsfsdfdsf sdf."
str.split( (/[\.\?\r\n]/g))
//["SDFDSFDSF", "sdf dsf sdfdsf", " sdfdsfsdfdsfdsfdsfdsfsdfdsf sdf", ""]
Use for each iteration capabilities like this:
breakitup.forEach(function(element){
var packagedtogo = document.createElement('span');
packagedtogo.className = 'sentence';
packagedtogo.innerHTML = element;//breakitup is undefiend
output.appendChild(packagedtogo);
//No need to increase index
});