<input type='file'/> で画像を選択させる input.onchange が発火するのでコールバックをとる File APIがあれば input.files[0] にFileオブジェクトが入ってるの抜き取る FileReader の FileReader#readAsDataURL に Fileオブジェクトを渡す FileRead#onload が発火するのでevent.target.result に Data uri が入ってる imgのsrcにData uri ぶち込む <img class='image-preview'/> <input type='file' class='file-selector'>upload</input> $preview = $('img.image-preview') $file = $('input.file-selector')
![HTML5 File API で画像をアップロードしてプレビュー - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/af057ffe0444fbda2383804ddd49369085681276/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-412672c5f0600ab9a64263b751f1bc81.png%3Fixlib%3Drb-4.0.0%26w%3D1200%26mark64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTk3MiZoPTM3OCZ0eHQ9SFRNTDUlMjBGaWxlJTIwQVBJJTIwJUUzJTgxJUE3JUU3JTk0JUJCJUU1JTgzJThGJUUzJTgyJTkyJUUzJTgyJUEyJUUzJTgzJTgzJUUzJTgzJTk3JUUzJTgzJUFEJUUzJTgzJUJDJUUzJTgzJTg5JUUzJTgxJTk3JUUzJTgxJUE2JUUzJTgzJTk3JUUzJTgzJUFDJUUzJTgzJTkzJUUzJTgzJUE1JUUzJTgzJUJDJnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9NTYmcz1mMDYzNGUxNjE3YTZlMTYxNWM1OTFkM2YzMjE0NDkwNQ%26mark-x%3D142%26mark-y%3D57%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZoPTc2Jnc9NzcwJnR4dD0lNDBtaXpjaGkmdHh0LWNvbG9yPSUyMzIxMjEyMSZ0eHQtZm9udD1IaXJhZ2lubyUyMFNhbnMlMjBXNiZ0eHQtc2l6ZT0zNiZ0eHQtYWxpZ249bGVmdCUyQ3RvcCZzPTM3NjdjNDAyYWFiOGYxMDdjNTcxNTJiZjU0ODYyN2Rh%26blend-x%3D142%26blend-y%3D436%26blend-mode%3Dnormal%26txt64%3DaW4g5qCq5byP5Lya56S-44OX44Os44Kk44OJ%26txt-width%3D770%26txt-clip%3Dend%252Cellipsis%26txt-color%3D%2523212121%26txt-font%3DHiragino%2520Sans%2520W6%26txt-size%3D36%26txt-x%3D156%26txt-y%3D536%26s%3Dfc8a5d49fc08f397208c1490eb7236b1)