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HTML5のフォームバリデーション
Table of contents
HTML5のフォームバリデーションで、ユーザーが正しいデータを入力しているのかをクライアントサイドで手軽に確認することができます。よく使われるバリデーションをいくつかご紹介します。
フィールドを入力必須にする![](data:image/svg+xml;base64,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)
required属性
を指定することで、フィールドを入力必須にできます。
<input type="text" name="message" required />
メールアドレスの書式を検証する![](data:image/svg+xml;base64,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)
input type="email"
を使うと、メールアドレスの書式が正しいかを検証できます。
<input type="email" name="email" />
URLの書式を検証する![](data:image/svg+xml;base64,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)
input type="url"
を使うと、URLの書式が正しいかを検証できます。
<input type="url" name="website" />
数値の最大値・最小値を指定する![](data:image/svg+xml;base64,PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPHN2ZyB3aWR0aD0iMjRweCIgaGVpZ2h0PSIyNHB4IiB2aWV3Qm94PSIwIDAgMjQgMjQiIHZlcnNpb249IjEuMSIgeG1sbnM9Imh0dHA6Ly93d3cudzMub3JnLzIwMDAvc3ZnIiB4bWxuczp4bGluaz0iaHR0cDovL3d3dy53My5vcmcvMTk5OS94bGluayI+CiAgICA8dGl0bGU+bGlua19ibGFja18yNGRwPC90aXRsZT4KICAgIDxnIGlkPSJQYWdlLTEiIHN0cm9rZT0ibm9uZSIgc3Ryb2tlLXdpZHRoPSIxIiBmaWxsPSJub25lIiBmaWxsLXJ1bGU9ImV2ZW5vZGQiPgogICAgICAgIDxnIGlkPSJsaW5rX2JsYWNrXzI0ZHAiIHRyYW5zZm9ybT0idHJhbnNsYXRlKDEyLjAwMDAwMCwgMTIuMDAwMDAwKSByb3RhdGUoLTQ1LjAwMDAwMCkgdHJhbnNsYXRlKC0xMi4wMDAwMDAsIC0xMi4wMDAwMDApIHRyYW5zbGF0ZSgyLjAwMDAwMCwgNy4wMDAwMDApIiBmaWxsPSIjMzMzMzMzIiBmaWxsLXJ1bGU9Im5vbnplcm8iPgogICAgICAgICAgICA8cGF0aCBkPSJNMTUsMy4zNzE5MTAyOGUtMTUgTDExLDMuMzcxOTEwMjhlLTE1IEwxMSwyIEwxNSwyIEMxNi42NSwyIDE4LDMuMzUgMTgsNSBDMTgsNi42NSAxNi42NSw4IDE1LDggTDExLDggTDExLDEwIEwxNSwxMCBDMTcuNzYsMTAgMjAsNy43NiAyMCw1IEMyMCwyLjI0IDE3Ljc2LDMuMzcxOTEwMjhlLTE1IDE1LDMuMzcxOTEwMjhlLTE1IFogTTksOCBMNSw4IEMzLjM1LDggMiw2LjY1IDIsNSBDMiwzLjM1IDMuMzUsMiA1LDIgTDksMiBMOSwzLjM3MTkxMDI4ZS0xNSBMNSwzLjM3MTkxMDI4ZS0xNSBDMi4yNCwzLjM3MTkxMDI4ZS0xNSAtMS41ODU3OTc0MmUtMTQsMi4yNCAtMS41ODU3OTc0MmUtMTQsNSBDLTEuNTg1Nzk3NDJlLTE0LDcuNzYgMi4yNCwxMCA1LDEwIEw5LDEwIEw5LDggWiBNNiw0IEwxNCw0IEwxNCw2IEw2LDYgTDYsNCBaIiBpZD0iU2hhcGUiPjwvcGF0aD4KICAgICAgICA8L2c+CiAgICA8L2c+Cjwvc3ZnPg==)
input type="number"
を使うと、max属性
とmin属性
で最大値・最小値を指定できます。
<input type="number" name="age" max="12" min="6" />
文字列の最大文字数・最小文字数を指定する![](data:image/svg+xml;base64,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)
maxlength属性
とminlength属性
で最大文字数・最小文字数を指定できます。input type="text"
及びtextarea
で有効です。
<input type="text" name="message" minlength="5" />
<textarea name="message" maxlength="140"></textarea>
ファイルの拡張子を制限する![](data:image/svg+xml;base64,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)
input type="file"
を使うと、accept属性
で許可するファイルのMIMEタイプおよび拡張子を指定できます。
<input type="file" accept=".jpg,.gif" />
正規表現を使って入力値のパターンを指定する![](data:image/svg+xml;base64,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)
pattern属性
で、入力値のパターンを正規表現で指定できます。
<!-- 例)半角英数字 -->
<input type="text" pattern="^[0-9A-Za-z]+$" />