JavaScript検証API
制約検証DOMメソッド
| Property | Description |
|---|---|
| checkValidity() | Returns true if an input element contains valid data. |
| setCustomValidity() | Sets the validationMessage property of an input element. |
入力フィールドに無効なデータが含まれている場合は、次のメッセージを表示します。
checkValidity（）メソッド
<input id="id1" type="number" min="100" max="300"
required>
<button onclick="myFunction()">OK</button>
<p id="demo"></p>
<script>
function myFunction() {
const inpObj = document.getElementById("id1");
if (!inpObj.checkValidity()) {
document.getElementById("demo").innerHTML = inpObj.validationMessage;
}
}
</script>
制約検証DOMプロパティ
| Property | Description |
|---|---|
| validity | Contains boolean properties related to the validity of an input element. |
| validationMessage | Contains the message a browser will display when the validity is false. |
| willValidate | Indicates if an input element will be validated. |
有効性プロパティ
input要素のvalidityプロパティには、データの有効性に関連するいくつかのプロパティが含まれています。
| Property | Description |
|---|---|
| customError | Set to true, if a custom validity message is set. |
| patternMismatch | Set to true, if an element's value does not match its pattern attribute. |
| rangeOverflow | Set to true, if an element's value is greater than its max attribute. |
| rangeUnderflow | Set to true, if an element's value is less than its min attribute. |
| stepMismatch | Set to true, if an element's value is invalid per its step attribute. |
| tooLong | Set to true, if an element's value exceeds its maxLength attribute. |
| typeMismatch | Set to true, if an element's value is invalid per its type attribute. |
| valueMissing | Set to true, if an element (with a required attribute) has no value. |
| valid | Set to true, if an element's value is valid. |
例
入力フィールドの数値が100（入力の属性）より大きい場合は、次max
のメッセージを表示します。
rangeOverflowプロパティ
<input id="id1" type="number" max="100">
<button onclick="myFunction()">OK</button>
<p id="demo"></p>
<script>
function myFunction() {
let text = "Value OK";
if (document.getElementById("id1").validity.rangeOverflow) {
text = "Value too large";
}
}
</script>
入力フィールドの数値が100（入力の属性）未満の場合は、次minのメッセージを表示します。
rangeUnderflowプロパティ
<input id="id1" type="number" min="100">
<button onclick="myFunction()">OK</button>
<p id="demo"></p>
<script>
function myFunction() {
let text = = "Value OK";
if (document.getElementById("id1").validity.rangeUnderflow) {
text = "Value too small";
}
}
</script>