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How to pass variable into a onclick function

I am wanting to try and pass record.ItemID to my onclick = buy() function. But I am getting errors like "Uncaught SyntaxError: Unexpected end of input"
I have tried \"record.ItemID \" but that of course just passes the literal string of result.name
I have also tried (\'' + record.ItemID + '\') but get the same Syntax error
function showShop(items) {
let tableContent = "<tr class='orderTitle'><td =imgTable></td><td id = contentTable ></td></tr>\n";
let odd = true;
const addRecord = (record) => {
tableContent += odd ? "<tr class='orderOdd'>" : "<tr class='orderEven'>";
odd = !odd;
tableContent += "<td>" + "<img id = image src="+ "http://redsox.uoa.auckland.ac.nz/ms/MuseumService.svc/shopimg?id=" + record.ItemId + " />" + "</td><td id = content>" + record.Description + "<td><button onclick='buy("+ record.ItemId +")'/> Buy </button></td>";
}
items.forEach(addRecord)
document.getElementById("shop").innerHTML = tableContent;
}
function buy(item){
window.open('http://redsox.uoa.auckland.ac.nz/mss/Service.svc/buy?id='+ item,'_self');
}

I'm not sure if this will solve your problem but it looks like you're mixing up 's and "s.
onclick='buy('record.ItemId')'
You are terminating the onclick attribute right after buy(.
You may need to do something like:
onclick='buy(" + record.ItemId + ")'
Generally speaking though, if you have to build up HTML in strings, you are better off string interpolation. It makes it easier to read and is less prone to these types of issues.
Example:
const html = `<button onclick="buy(${record.ItemId})">Click</button>`;

It looks like you're trying to build up some HTML content to put into a table, and you want some behaviour attached to a button inside the table so that it opens a new window when you click on it.
There are a number of different approaches to what you're trying to do which would be safer in production code, so while you've got some answers to your specific question, please consider these alternative approaches which are more idiomatic:
You could use a link (<a>) instead of a button, and use CSS to make the link look like a button. This avoids needing a click handler at all.
You could use data attributes to store the record in a safe way, then access it from the click event, e.g. e.target.dataset.recordId.
You could use jQuery or a similar toolkit to create the button, then attach a function to the button as a click handler.
When you create HTML directly like you are doing in your question, you're opening your code up to code injection, where someone malicious could craft data that could steal private information from users of your site. It's much safer to use a library to construct your HTML directly rather than building it up in strings.

Really you're much better off separating out your inline JS and using event listeners to target classes on your elements.
Here's a quick example to show you how you might achieve that:
const records = [{ itemId: 1 }, { itemId: 2 }, { itemId: 3 }];
const imgRoot = 'https://dummyimage.com/30x30/676767/fff.png?id=';
// `map` iterates over the array and produces one element of HTML per record
// We use a class on the button to identify it, and a data attribute
// button to hold the itemId
const html = records.map(({ itemId }) => {
return `
<div class="itemWrapper">
<img class="item" src="${imgRoot}${itemId}" />
<button data-itemid="${itemId}" class="buyRecord">Buy record</button>
</div>
`;
});
document.querySelector('.root').innerHTML = html.join('');
// We grab the buttons and iterate over them attaching
// event listeners that call `handleBuy` when the button is clicked
const buyButtons = document.querySelectorAll('.buyRecord');
buyButtons.forEach(button => button.addEventListener('click', handleBuy, false));
function handleBuy(e) {
// Destructure the itemid from the dataset of the button
// click event
const { target: { dataset: { itemid } } } = e;
console.log(itemid);
}
<div class="root" />
Documentation
map
Data attributes
Template literals
Destructuring assignment

The General format of onclick is
onclick="function_name(variable)"
For this case you can do something like this:
tableContent += '<td>' + '<img id = image src="http://redsox.uoa.auckland.ac.nz/ms/MuseumService.svc/shopimg?id=' + record.ItemId + '" /></td><td id="content">' + record.Description + '<td><button onclick="buy('+record.ItemId+')"> Buy </button></td>';

executing JS function and define variable from html

What I have is a page which is gathering a large list of data via jQuery. I am trying to limit the amount of results shown to a variable, and change the results shown on the list to create a false-page effect. Everything works via the same JS function, and relies on 1 variable to make everything work. Simple. I've removed all of the extra code to simplify everything
function myFunction() { var page = 1; console.log(page); }
I am looking for a way to call on this function, but change the variable 'page' from within html. Something along the lines of:
2
I have been looking on google (and still am) I just can't seem to find what I am looking for. I'm trying to avoid multiple pages/refreshing as this element is going to be used for a larger project on the same page.
UPDATE: I managed to pass the intended values through to a JS function like so...
function myFunction(page) { console.log(page); }
...and...
<input type='button' onclick='myFunction(value)' value='input page number'>
This seems the simplest way of doing what I need, what do you think?
Thanks for your help btw guys.

To do this you will need to move the page variable to be a parameter of myFunction
function myFunction(page) { console.log(page); }
Then you can just pass in whatever page number you would like
2

Sure, you can add the data-url attribute to your markup and select on the .link class to fetch the data-url attribute for each element thats part of that class.
I'm trying to avoid multiple pages/refreshing as this element is going
to be used for a larger project on the same page.
Sounds like you also want an AJAX solution.
$(document).ready( function()
{
//Add this on your call.html page
$(".link").click(function()
{
//location of test JSON file
var root = 'https://jsonplaceholder.typicode.com';
//your custom attribute acting as your 'variable'
var page = $(this).attr('data-url');
console.log("page = " + page);
//remove any previous html from the modal
$(".modal-content").empty();
//send a request to the server to retrieve your pages
$.ajax(
{
method: "GET",
//this should be updated with location of file
url: root + '/posts/' + page,
//if server request to get page was successful
success: function(result)
{
console.log(result);
var res = result;
var content = "<div class='panel-default'><div class='panel-heading'><h3 class='panel-title'>" + res.title + "</h3></div><i><div class='panel-body'>''" + res.body + "''</i></div><p><u> Master Yoda, (2017)</u></p><p class='page'> Page: " + page + "</p></div>";
$(".modal-content").html(content);
},
//otherwise do this
error: function(result)
{
$(".modal-content").html("<div class='error'><span><b> Failed to retrieve data </b></span><p> try again later </p></div>");
}
});
});
});
.error
{
border: 2px dotted red;
margin: 5px;
}
a
{
font-size: 20px;
}
.page
{
text-align: left;
padding: 0 15px;
}
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet" />
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.5/js/bootstrap.min.js"></script>
<a class="link" data-url="1" data-toggle="modal" data-target="#Modal" href="test.html">Show Page 1</a>
<br />
<a class="link" data-url="2" data-toggle="modal" data-target="#Modal" href="">Show Page 2</a>
<div id="Modal" class="modal fade text-center">
<div class="modal-dialog">
<div class="modal-content">
</div>
</div>
</div>

I seem to have figured out how to do this. I wanted to stray from using lots of libraries in the project and just wanted to keep things simple, using the above answers for guidance (and a little more digging), basically my end goal was to use jQuery to obtain a long list of data, and format this data into a multiple page list (for which I used a table for formatting purposes). Let's say it's a list of names. The JSON results output as:
[{"first_name":"Bob"},{"last_name":"Jones"}] // (key, value)
But when I passed this through to the HTML Table it was just displaying 1000s of results in a single list, and formatting the list was a pain. This was my solution:
<script>
var pageNum = ""; // define Page Number variable for later.
var resLimit = 35; // variable to specify the number of results per page
function updateList () {
$.getJSON(" Location of JSON results ", function(data) {
var pageCount = Math.round(data.length/resLimit); // calculate number of pages
var auto_id = ((pageNum-1)*resLimit) // use variables to give each result an id
var newListData = ""; // define this for use later
then define and pass "new list data" to HTML Table:
var newListData = "";
$.each(data.slice(auto_id, (pageNum*resLimit)), function(key, value) {
auto_id++;
newListData += '<tr>';
newListData += '<td class="id">' + audo_id + '</td>';
newListData += '<td class="id">' + value.first_name + '</td>';
newListData += '<td class="id">' + value.last_name + '</td>';
newListData += '</tr>';
});
$('# ID of table, data will replace existing rows ').html(newListData);
At this point if you set the value of pageNum to 1 you should see the first 35 results on the list, all with auto-incremented ID numbers. If you change it to 2 and refresh the page you should see the next 35, with the ID numbers following on from the first page.
Next I needed to create a button for each of the pages:
$('# ID of table, data will replace existing rows ').html(newListData);
function createButtons() {
var buttonArray = "";
for(i=0, x=pageCount; i<x; i++) {
buttonArray += '<input type="button" onclick="changePage('
+ (i + 1) + ')" value="' + (i + 1) + '">';
}
$('# ID of Span tags for button container ').html(buttonArray); }
createButtons();
}); }
</script>
Then create changePage() and a function to refresh the data in the list automatically without messing things up
<script>
var pageNum = "";
function changePage(page) {
if (pageNum < 1) { pageNum = 1; } // set pageNum when the page loads
if (page > 0) { pageNum = page; } // overwrite pageNum when 'page' variable is defined
updateList(); }
changePage(); // initialise to prevent delayed display on page load
// refresh function:
function refreshData() {
changePage(0); // define 'page' as 0 so that pageNum is not overwritten
window.setTimeout(refreshData, 5000); } // loop this function every 5 seconds to
refreshData(); //-- keep this list populated with current data.
And that should just about do it! At least it's working for me but I might have missed something (hopefully not lol). Hope this helps someone theres quite a few things involved in this that could be extrapolated and used elsewhere :)
thanks for help everyone.

How to properly generate HTML in a JavaScript widget?

I've been following this tutorial on how to make JS widget. However I noticed that manually building html with plain JavaScript is not DRY. I am planning to build a form, tables etc. in a JS widget. Whats the best way to do this?
$.getJSON(jsonp_url, function(data) {
var fruits = ["Apples", "Mangoes", "Banana"];
var myHtml = "<ul>";
$(fruits).each(function(i){
myHtml += "<li>" + fruits[i] + "</li>";
});
myHtml += "</ul>";
$('#example-widget-container').html(myHtml);
});

if you want one of your divs or containers to continuously grow while you build dynamic content, without losing older content, use jQuery.append
$('#example-widget-container').append(myHtml);
this is probably the cleanest way. Or you can do other things like
var html = $('#example-widget-container').html();
newHtml = yourContent;
$('#example-widget-container').html(html + newHtml);

In JavaScript you can generate html content in different ways :
Create HTML with a string directly :
$("#sampleArea").append('<div class="' + newClass + '">' + newText + '</div>');
Create HTML with jQuery Api wrapping :
$("#sampleArea").append($('<div/>',{class : newClass}).text(newText));
Use a template engine in Javascript (like mustache.js) :
<script id="exampleTpl" type="x-tmpl-mustache">
<div class="{{class}}">{{text}}</div>
</script>
<script>
var data = {
class: newClass,
text: newText
}
var template = $('#exampleTpl').html();
var html = Mustache.render(template, data);
$('#sampleArea').append(html);
</script>
The best solution will depends of your use.

edit (append?) a string stored in a jquery variable

I am bringing a big html string inside an ajax call that I want to modify before I use it on the page. I am wondering if it is possible to edit the string if i store it in a variable then use the newly edited string. In the success of the ajax call this is what I do :
$.each(data.arrangement, function() {
var strHere = "";
strHere = this.htmlContent;
//add new content into strHere here
var content = "<li id=" + this.id + ">" + strHere + "</li>";
htmlContent is the key for the chunk of html code I am storing in the string. It has no problem storing the string (I checked with an alert), but the issue is I need to target a div within the stored string called .widgteFooter, and then add some extra html into that (2 small divs). Is this possible with jquery?
Thanks

Convert the string into DOM elements:
domHere = $("<div>" + strHere + "</div>");
Then you can update this DOM with:
$(".widgetFooter", domHere).append("<div>...</div><div>...</div>");
Then do:
var content = "<li id=" + this.id + ">" + domHere.html() + "</li>";

An alternative way to #Barmar's would be:
var domHere = $('<div/>').html( strHere ).find('.widgetFooter')
.append('<div>....</div>');
Then finish with:
var content = '<li id="' + this.id + '">' + domHere.html() + '</li>';

You can manipulate the string, but in this case it's easier to create elements from it and then manipulate the elements:
var elements = $(this.htmlContent);
elements.find('.widgteFooter').append('<div>small</div><div>divs</div>');
Then put the elements in a list element instead of concatenating strings:
var item = $('<li>').attr('id', this.id).append(elements);
Now you can append the list element wherever you did previously append the string. (There is no point in turning into a string only to turn it into elements again.) Example:
$('#MyList').append(item);

Pass string from one function to the next javascript

I've got a simple JavaScript client that pulls from a REST API to present some book data, however I seem unable to call the function createBookRow(bookid) and return the appropriate html string to the document ready function where it is called,
The output is currently being produced correctly as verified by the append to .row-fluid on the html page, ideas or suggestions welcome
function createBookRow(bookid)
{
$.get('http://mysite.co.uk/atiwd/books/course/'+bookid+'/xml', function(xml){
$(xml).find('book').each(function(){
var $book = $(this);
var id = $book.attr("id");
var title = $book.attr("title");
var isbn = $book.attr("isbn");
var borrowedcount = $book.attr("borrowedcount");
var html = '<div class="span3"><img name="test" src="http://covers.openlibrary.org/b/isbn/'+isbn+'-L.jpg" width="32" height="32" alt=""></p>' ;
html += '<p> ' + title + '</p>' ;
html += '<p> ' + isbn + '</p>' ;
html += '<p> ' + borrowedcount + '</p>' ;
html += '</div>';
$('.row-fluid').append($(html));
});
});
}
$(document).ready(function()
{
$.get('xml/courses.xml', function(xml){
$(xml).find('course').each(function(){
var $course = $(this);
var id = $course.attr("id");
var title = $course.text();
var html = '<div class="span12"><p>' + title + '</p><row id="'+id+'" >'+createBookRow(id)+'</row></div>' ;
$('.row-fluid').append($(html));
$('.loadingPic').fadeOut(1400);
});
});
});

The line
var html = '<div class="span12"><p>' + title + '</p><row id="'+id+'" >'+createBookRow(id)+'</row></div>' ;
should be just
var html = '<div class="span12"><p>' + title + '</p><row id="'+id+'" ></row></div>' ;
createBookRow(id);
createBookRow(id) function is making a get request to get some details, which happens asynchronously. Unless you explicitly mention it is a synchronous call(which is not advised).
I guess the functionality you need is to render some rows for course and in between you need books details displayed. In that case you need to explicitly say where your book row needs to be appended.
$('.row-fluid').append($(html));
The above code will always append book row at the end.

You aren't returning anything in the code you provided. You just append some HTML to a jQuery object. Try adding a return statement
return html;