Inserts an HTML string before the start of the specified element.

Use el.insertAdjacentHTML() with a position of 'beforebegin' to parse htmlString and insert it before the start of el.

代码片段

const insertBefore = (el, htmlString) => el.insertAdjacentHTML('beforebegin', htmlString);

使用样例

insertBefore(document.getElementById('myId'), '<p>before</p>');
// <p>before</p> <div id="myId">...</div>