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Javascript - How can I replace text in HTML with text in script

I am new to javascript. I was thinking getelementbyid but i don't know how to make it work
Like the title, here is what I mean
For example I have in HTML:
<p>fw_93</p>
<p>fw_94</p>
<p>fw_93</p>
So what I want is to make script to replace those fw_93 fw_94 to what I want.
For example
Instead of displaying "fw_93" I want it to display "9.3". Same with fw_94 to 9.4

Replace fw_ with nothing, divide the number by 10:
Array.prototype.forEach.call(document.getElementsByTagName('p'), function(el) {
el.innerHTML = parseInt(el.innerHTML.replace(/[A-Za-z_]*/, '')) / 10;
});
<p>fw_93</p>
<p>fw_94</p>
<p>fw_93</p>

Okay so select the tags.
Loop over the collection
read the html
match the string
replace the html
var ps = document.querySelectorAll("p");
for (var i=0; i<ps.length; i++) {
var p = ps[i];
var txt = p.innerHTML; //.textContent
var updated = txt.replace(/.+(\d)(\d)/, "$1.$2");
p.innerHTML = updated;
}
<p>fw_93</p>
<p>fw_94</p>
<p>fw_93</p>

Using JQuery
Not sure why I did it with JQuery, guess I wasn't paying enough attention. No point in me re-writing as there are already good answers in JS. Though I will leave this in case it's of use to anyone that is using JQuery.
You can loop though each <p> element and covert the contents, something like this:
$("p").each(function() {
var text = $(this).html();
var text = text.substring(text.indexOf("_") + 1);
var text = text[0] + "." + text.substring(1);
$(this).html(text);
})
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<p>fw_93</p>
<p>fw_94</p>
<p>fw_93</p>
You may need to add validation depending on how reliable your input is.
Note that the code makes the following assumptions:
There will always be a _ followed by at least 2 digits
The . will always go after the first digit

Your HTML:
<p id="p1">init_value</p>
Your JS:
document.getElementById("p1").innerHTML = "new_value";

Find surrounding characters of an element inside a paragraph

I have this little problem. I need to find the first 3 characters before and after an anchor tag that is inside a paragraph.
Example:
<p>This is <a href='#' id='lock'>a</a> test for an anchor</p>
What I need to have as a result is:
is te
Where is (includes space at the end) is the first 3 characters left from the anchor tag and te (again including space at start) are the 3 first characters right from the anchor tag.
JQuery can help and so far I tried with regex and Jquery but no luck.
What else should I try? Is there something I might be missing?
It had been a while since I worked with frontend problems.

Something like this
var lock = document.getElementById('lock');
var prev = lock.previousSibling;
var next = lock.nextSibling;
var text = prev.textContent.slice(-3) + next.textContent.slice(0, 3);
FIDDLE

Use the following regex to capture the there characters before and after anchor a tag,
(.{3})<a href.*?<\/a>(.{3})
DEMO
If you want to replace the whole with only the captured groups then your regex would be,
.*(.{3})<a href.*?<\/a>(.{3}).*
And the substitution would be,
$1$2
DEMO
And your code would be,
> var str = "<p>This is <a href='#' id='lock'>a</a> test for an anchor</p>";
undefined
> var r = str.replace(/.*(.{3})<a href.*?<\/a>(.{3}).*/g, "$1$2");
undefined
> console.log(r);
is te
undefined

Try to use .contents() to grab the text nodes,
var pTag = $('p').contents();
console.log(pTag[0].nodeValue.slice(-3) +
pTag[2].nodeValue.substring(0,3)); // "is te"
DEMO

Another solution with jQuery and DOM traversing:
var a = $("a", "<p>This is <a href='#'>a</a> test for an anchor</p>")[0],
left = a.previousSibling.nodeValue.slice(-3),
right = a.nextSibling.nodeValue.slice(0, 3);
console.log(left, right); // "is " " te"

JAVASCRIPT - if last character is : (colon), change font weight

Is it possible to change font weight if last character is colon with JavaScript?
I have site, where people can add recipe. And i want to highlight parts of ingredients of recipe. For example:
topping:
-chocolate
-milk
filling:
-...
-...
I searched and i found that codes:
for last character
if (myString.charAt(myString.length - 1) == ':')
and for weight change
function changeWeight(600)
{
document.getElementById("id_1").style.fontWeight = fontWeight;
}
I do not know how to write the code to work. I am beginner.
Thank you very much.

Try this
if (myString.charAt(myString.length - 1) == ':') {
changeWeight("600");
}
function changeWeight(weight) {
document.getElementById("id_1").style.fontWeight = weight;
}

It seems that you want to make specific text bold, not all text within an element. You would need to get the text out of the element, change it, and put it back.
You can use code like this to but a bold tag around all words in the element that ends with a colon:
var element = document.getElementById("id_1");
var text = element.innerHTML;
text = text.replace(/([A-Za-z]+:)/g, '<strong>$1</strong>');
element.innerHTML = text;
Note: For that to work properly, you can't have other HTML elements inside the element that has words with colons in the actual markup. I you have for example SO in the code, it would break because of the http: in the link.
If you have that single word alone in an element, you would get the text and check for the colon:
var element = document.getElementById("id_1");
var text = element.innerHTML;
if (text.charAt(text.length - 1)) == ':') {
element.style.fontWeight = 'bold';
}

JavaScript RegExp match text ignoring HTML

Is it possible to match "the dog is really really fat" in "The <strong>dog</strong> is really <em>really</em> fat!" and add "<span class="highlight">WHAT WAS MATCHED</span>" around it?
I don't mean this specifically, but generally be able to search text ignoring HTML, keeping it in the end result, and just add the span above around it all?
EDIT:
Considering the HTML tag overlapping problem, would it be possible to match a phrase and just add the span around each of the matched words? The problem here is that I don't want the word "dog" matched when it's not in the searched context, in this case, "the dog is really really fat."

Update:
Here is a working fiddle that does what you want. However, you will need to update the htmlTagRegEx to handle matching on any HTML tag, as this just performs a simple match and will not handle all the cases.
http://jsfiddle.net/briguy37/JyL4J/
Also, below is the code. Basically, it takes out the html elements one by one, then does a replace in the text to add the highlight span around the matched selection, and then pushes back in the html elements one by one. It's ugly, but it's the easiest way I could think of to get it to work...
function highlightInElement(elementId, text){
var elementHtml = document.getElementById(elementId).innerHTML;
var tags = [];
var tagLocations= [];
var htmlTagRegEx = /<{1}\/{0,1}\w+>{1}/;
//Strip the tags from the elementHtml and keep track of them
var htmlTag;
while(htmlTag = elementHtml.match(htmlTagRegEx)){
tagLocations[tagLocations.length] = elementHtml.search(htmlTagRegEx);
tags[tags.length] = htmlTag;
elementHtml = elementHtml.replace(htmlTag, '');
}
//Search for the text in the stripped html
var textLocation = elementHtml.search(text);
if(textLocation){
//Add the highlight
var highlightHTMLStart = '<span class="highlight">';
var highlightHTMLEnd = '</span>';
elementHtml = elementHtml.replace(text, highlightHTMLStart + text + highlightHTMLEnd);
//plug back in the HTML tags
var textEndLocation = textLocation + text.length;
for(i=tagLocations.length-1; i>=0; i--){
var location = tagLocations[i];
if(location > textEndLocation){
location += highlightHTMLStart.length + highlightHTMLEnd.length;
} else if(location > textLocation){
location += highlightHTMLStart.length;
}
elementHtml = elementHtml.substring(0,location) + tags[i] + elementHtml.substring(location);
}
}
//Update the innerHTML of the element
document.getElementById(elementId).innerHTML = elementHtml;
}

Naah... just use the good old RegExp ;)
var htmlString = "The <strong>dog</strong> is really <em>really</em> fat!";
var regexp = /<\/?\w+((\s+\w+(\s*=\s*(?:\".*?"|'.*?'|[^'\">\s]+))?)+\s*|\s*)\/?>/gi;
var result = '<span class="highlight">' + htmlString.replace(regexp, '') + '</span>';

A simpler way with JQuery would be.
originalHtml = $("#div").html();
newHtml = originalHtml.replace(new RegExp(keyword + "(?![^<>]*>)", "g"), function(e){
return "<span class='highlight'>" + e + "</span>";
});
$("#div").html(newHtml);
This works just fine for me.

Here is a working regex example to exclude matches inside html tags as well as javascripts:
http://refiddle.com/lwy6
Use this regex in a replace() script.
/(a)(?!([^<])*?>)(?!<script[^>]*?>)(?![^<]*?<\/script>|$)/gi

this.keywords.forEach(keyword => {
el.innerHTML = el.innerHTML.replace(
RegExp(keyword + '(?![^<>]*>)', 'ig'),
matched => `<span class=highlight>${matched}</span>`
)
})

You can use string replace with this expression </?\w*> and you'll get your string

If you use jQuery, you can use the text property on the element containing the text you're searching for. Given this markup:
<p id="the-text">
The <strong>dog</strong> is really <em>really</em> fat!
</p>
This would yield "The dog is really really fat!":
$('#the-text').text();
You could do your regex search on that text instead of trying to do so in the markup.
Without jQuery, I'm unsure of an easy way to extract and concatenate the text nodes from all child elements.

JavaScript to add HTML tags around content

I was wondering if it is possible to use JavaScript to add a <div> tag around a word in an HTML page.
I have a JS search that searches a set of HTML files and returns a list of files that contain the keyword. I'd like to be able to dynamically add a <div class="highlight"> around the keyword so it stands out.
If an alternate search is performed, the original <div>'s will need to be removed and new ones added. Does anyone know if this is even possible?
Any tips or suggestions would be really appreciated.
Cheers,
Laurie.

In general you will need to parse the html code in order to ensure that you are only highlighting keywords and not invisible text or code (such as alt text attributes for images or actual markup). If you do as Jesse Hallett suggested:
$('body').html($('body').html().replace(/(pretzel)/gi, '<b>$1</b>'));
You will run into problems with certain keywords and documents. For example:
<html>
<head><title>A history of tables and tableware</title></head>
<body>
<p>The table has a fantastic history. Consider the following:</p>
<table><tr><td>Year</td><td>Number of tables made</td></tr>
<tr><td>1999</td><td>12</td></tr>
<tr><td>2009</td><td>14</td></tr>
</table>
<img src="/images/a_grand_table.jpg" alt="A grand table from designer John Tableius">
</body>
</html>
This relatively simple document might be found by searching for the word "table", but if you just replace text with wrapped text you could end up with this:
<<span class="highlight">table</span>><tr><td>Year</td><td>Number of <span class="highlight">table</span>s made</td></tr>
and this:
<img src="/images/a_grand_<span class="highlight">table</span>.jpg" alt="A grand <span class="highlight">table</span> from designer John <span class="highlight">Table</span>ius">
This means you need parsed HTML. And parsing HTML is tricky. But if you can assume a certain quality control over the html documents (i.e. no open-angle-brackets without closing angle brackets, etc) then you should be able to scan the text looking for non-tag, non-attribute data that can be further-marked-up.
Here is some Javascript which can do that:
function highlight(word, text) {
var result = '';
//char currentChar;
var csc; // current search char
var wordPos = 0;
var textPos = 0;
var partialMatch = ''; // container for partial match
var inTag = false;
// iterate over the characters in the array
// if we find an HTML element, ignore the element and its attributes.
// otherwise try to match the characters to the characters in the word
// if we find a match append the highlight text, then the word, then the close-highlight
// otherwise, just append whatever we find.
for (textPos = 0; textPos < text.length; textPos++) {
csc = text.charAt(textPos);
if (csc == '<') {
inTag = true;
result += partialMatch;
partialMatch = '';
wordPos = 0;
}
if (inTag) {
result += csc ;
} else {
var currentChar = word.charAt(wordPos);
if (csc == currentChar && textPos + (word.length - wordPos) <= text.length) {
// we are matching the current word
partialMatch += csc;
wordPos++;
if (wordPos == word.length) {
// we've matched the whole word
result += '<span class="highlight">';
result += partialMatch;
result += '</span>';
wordPos = 0;
partialMatch = '';
}
} else if (wordPos > 0) {
// we thought we had a match, but we don't, so append the partial match and move on
result += partialMatch;
result += csc;
partialMatch = '';
wordPos = 0;
} else {
result += csc;
}
}
if (inTag && csc == '>') {
inTag = false;
}
}
return result;
}

Wrapping is pretty easy with jQuery:
$('span').wrap('<div class="highlight"></div>'); // wraps spans in a b tag
Then, to remove, something like this:
$('div.highlight').each(function(){ $(this).after( $(this).text() ); }).remove();
Sounds like you will have to do some string splitting, though, so wrap may not work unless you want to pre-wrap all your words with some tag (ie. span).

The DOM API does not provide a super easy way to do this. As far as I know the best solution is to read text into JavaScript, use replace to make the changes that you want, and write the entire content back. You can do this either one HTML node at a time, or modify the whole <body> at once.
Here is how that might work in jQuery:
$('body').html($('body').html().replace(/(pretzel)/gi, '<b>$1</b>'));

couldn't you just write a selector as such to wrap it all?
$("* :contains('foo')").wrap("<div class='bar'></div>");
adam wrote the code above to do the removal:
$('div.bar').each(function(){ $(this).after( $(this).text() ); }).remove();
edit: on second thought, the first statement returns an element which would wrap the element with the div tag and not the sole word. maybe a regex replace would be a better solution here.