js通过name属性获取值

// HTML 示例
// <input type="text" name="username" value="JohnDoe">

// JavaScript 代码
var elements = document.getElementsByName('username');
if (elements.length > 0) {
    var value = elements[0].value; // "JohnDoe"
    console.log(value);
}

// HTML 示例
// <input type="text" name="username" value="JohnDoe">

// JavaScript 代码
var element = document.querySelector('input[name="username"]');
if (element) {
    var value = element.value; // "JohnDoe"
    console.log(value);
}

var elements = document.getElementsByName('username');
if (elements.length > 0) {
    var value = elements[0].value;
    console.log(value);
}

document.addEventListener('DOMContentLoaded', function() {
    var element = document.querySelector('input[name="username"]');
    if (element) {
        var value = element.value;
        console.log(value);
    } else {
        console.log('Element not found');
    }
});