Suppose I have a textarea element in my HTML and I want to adjust its height based on the content after it loads. How to do it? 1. The textarea element I defined is as follows Note: id = 'value' The key question here is There are two methods to determine which function will be called after the html is loaded: 2.1 Method 1: By calling $(document).ready(function () {} ) function get_text_rows(text) { return text.split("\n").length; } $(document).ready(function () { document.getElementById('value').rows = get_text_rows($('#value').val()); }); 2.2 Method 2: By calling window.onload function get_text_rows(text) { return text.split("\n").length; } window.onload = function() { document.getElementById('value').rows = get_text_rows($('#value').val()); }