To make text bold in JavaScript, do this:
element.style.fontWeight = 'bold'.For example, if this is your element:
<div id="my-element">text</div>
Then you can make the text inside this element bold like so:
document.getElementById('my-element').style.fontWeight = 'bold';
And you can do the same with the style attribute in HTML:
<div id="my-element" style="font-weight: bold">text</div>