js取得select默认值

// HTML
<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2" selected>Option 2</option>
  <option value="3">Option 3</option>
</select>

// JavaScript
const selectElement = document.getElementById('mySelect');
const defaultValue = selectElement.value;
console.log(defaultValue); // 输出: "2"

// HTML
<select id="mySelect">
  <option value="1">Option 1</option>
  <option value="2" selected>Option 2</option>
  <option value="3">Option 3</option>
</select>

// JavaScript
const selectElement = document.getElementById('mySelect');
let defaultValue;

for (let i = 0; i < selectElement.options.length; i++) {
  if (selectElement.options[i].selected) {
    defaultValue = selectElement.options[i].value;
    break;
  }
}

console.log(defaultValue); // 输出: "2"

window.onload = function() {
  const selectElement = document.getElementById('mySelect');
  const defaultValue = selectElement.value;
  console.log(defaultValue);
};