Insert given HTML before an element

Parse an HTML string and insert it before the element.

JavaScriptBrowser · DOM Version 1.0.0 · MIT · .md

function insertHtmlBefore(html, element) { element.insertAdjacentHTML('beforebegin', html); }

Usage

Markup

<p id="intro">Intro</p>

Script

insertHtmlBefore('<h2>Title</h2>', document.querySelector('#intro'));
document.querySelector('#intro').previousElementSibling.tagName; // → 'H2'

Lines marked → were executed in headless Chromium against the markup above, and each result was compared with the value shown. Lines marked e.g. are illustrative.

Know the limits

• The string is parsed as HTML: never pass user input (XSS). Inserted script elements do not run, but inline event handlers such as onerror do.
• The element needs a parent for beforebegin and afterend positions.

The function above is the code the usage lines run. It does not validate its arguments; add checks where it receives untrusted input.

Keep exploring

• Check if a given DOMRect is contained within another DOMRect — True when the target lies inside the container or on its edges.
• Check if two DOMRects intersect — Two rects intersect when they meet on both axes.
• Compare two DOMRects for size and position match — Compare x, y, width and height exactly.