Uncaught SyntaxError: '' string literal contains an unescaped line break

you mix up php and javascript here:

echo '<li onclick="updateBasket('.$i.','+value['basketID'].')"><?= $i ?></li>';

you are still in php context, when using <?= $i ?> the value['basketId'] has to be evaluated in JS? dont you have that basketId variable present in php?

//this just echoes out `value['basketId']`, but i am not sure it will work as you expect
echo '<li onclick="updateBasket(' . $i . ', value[\'basketID\'])">' . $i . '</li>'; 

//this should work when you have the `$basketId` in php
echo '<li onclick="updateBasket(' . $i . ', ' . $basketId . ')">' . $i . '</li>';

but i strongly suggest to refactor all of that code, you are in JS context printing HTML using PHP that prints HTML and JS 🤯

Please show the actual code instead of a copy/paste from the error.

@sinnbeck

have you tried this?

echo '<li onclick="updateBasket(' . $i . ', value[\'basketID\'])">' . $i . '</li>'; 

i suggest at least switching from php to javascript when using the for loop

var tr = '<tr>\n' + 
//... +
'<ul>';

var i;
for (i = 1; i < 31; i++) {
  tr += '<li onclick="updateBasket(' + i + ', ' + value['basketID'] + ')">' + i + '</li>';
}
tr += '</ul>';

at least make this work and then try a find a totally different approach

@sinnbeck It's his actual code what is sad.

You can also use template laterals in javascript e.g

let cardAboutBusiness = `{{ $features->content }}`;
$("[design-business-about]").html(cardAboutBusiness)