フォームの要素を取得する
<form name="formName" action="">
<div>
<h3>text</h3>
<input name="textName" type="text" value="hello,JavaScript form!" />
</div>
<div>
<h3>radio</h3>
<input name="radioName" type="radio" value="1" />item 1
<input name="radioName" type="radio" value="2" />item 2
<input name="radioName" type="radio" value="3" checked />item 3
</div>
<div>
<h3>checkbox</h3>
<input name="checkboxA" type="checkbox" checked />check A
<input name="checkboxB" type="checkbox" />check B
</div>
<div>
<h3>select</h3>
<select name="selectName">
<option value="1">selection 1</option>
<option value="2" selected>selection 2</option>
<option value="3">selection 3</option>
</select>
</div>
<div>
<h3>textArea</h3>
<textarea name="textAreaName">write some text here.</textarea>
</div>
<div>
<h3>button</h3>
<input name="buttonName" type="button" value="button222" />
</div>
</form>
document.forms.formName.buttonName.addEventListener("click", function () {
console.log("CLICKED");
document.forms.formName.textName.value = "changed!!";
document.forms.formName.radioName.value = "1";
document.forms.formName.selectName.value = "1";
document.forms.formName.checkboxB.checked = "true";
document.forms.formName.textAreaName.value = "changed!!!";
});
セレクトボックスで選択されているオプション番号を取得する selectedIndex
