我有点惊讶，因为下面没有人提到解决方案。

通过document.forms.namedItem函数获取表单数据

var form = document.forms.namedItem("fileinfo");

form.addEventListener('submit', function(ev) {
   var oData = new FormData(form);
}

HT的

<form name="fileinfo">
  <label>Your email address:</label>
  <input type="email" autocomplete="on" autofocus name="userid" placeholder="email" required size="32" maxlength="64" /><br />
  <label>Custom file label:</label>
  <input type="text" name="filelabel" size="12" maxlength="32" /><br />
  <label>File to stash:</label>
  <input type="file" name="file" required />
  <input type="submit" value="Stash the file!" />
</form>
<div></div>

这是我的香草JS版本(在Chrome上测试)

适用于:

name = "输入" Name ="form[Name]"(创建一个对象) Name ="checkbox[]"(创建一个数组对象) Name ="form[checkbox][]"(创建一个数组) Name ="form[select][Name]"(创建一个只包含所选值的对象)

/**
 * Get the values from a form
 * @param formId ( ID without the # )
 * @returns {object}
 */
function getFormValues( formId )
{
    let postData = {};
    let form = document.forms[formId];
    let formData = new FormData( form );

    for ( const value of formData.entries() )
    {
        let container = postData;
        let key = value[0];
        let arrayKeys = key.match( /\[[\w\-]*\]/g ); // Check for any arrays

        if ( arrayKeys !== null )
        {
            arrayKeys.unshift( key.substr( 0, key.search( /\[/ ) ) );  // prepend the first key to the list
            for ( let i = 0, count = arrayKeys.length, lastRun = count - 1; i < count; i++ )
            {
                let _key = arrayKeys[i];
                _key = _key.replace( "[", '' ).replace( "]", '' ); // Remove the brackets []
                if ( _key === '' )
                {
                    if ( ! Array.isArray( container ) )
                    {
                        container = [];
                    }

                    _key = container.length;
                }

                if ( ! (_key in container) ) // Create an object for the key if it doesn't exist
                {
                    if ( i !== lastRun && arrayKeys[i + 1] === '[]' )
                    {
                        container[_key] = [];
                    }
                    else
                    {
                        container[_key] = {};
                    }
                }

                if ( i !== lastRun ) // Until we're the last item, swap container with it's child
                {
                    container = container[_key];
                }

                key = _key;
            }
        }
        container[key] = value[1]; // finally assign the value
    }

    return postData;
}

$("#form input, #form select, #form textarea").each(function() {
 data[theFieldName] = theFieldValue;
});

除此之外，你可能想看看serialize();

$('form').serialize() //this produces: "foo=1&bar=xxx&this=hi"

demo

现在是2019年，有一个更好的方法:

const form = document.querySelector('form');
const data = new URLSearchParams(new FormData(form).entries());

或者如果你想要一个普通的对象

const form = document.querySelector('form');
const data = Object.fromEntries(new FormData(form).entries());

尽管请注意，这将不适用于重复的键，如您从多选和重复的复选框具有相同的名称。

这将把所有表单字段附加到JavaScript对象“res”:

var res = {};
$("#form input, #form select, #form textarea").each(function(i, obj) {
    res[obj.name] = $(obj).val();
})