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HTML

CSS

CSS Base

Vendor Prefixing

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JavaScript

Babel includes JSX processing.

Add External Scripts/Pens

Any URL's added here will be added as <script>s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.

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Packages

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HTML

              
                <div id="app">
    <img src="https://picsum.photos/id/1008/1920/1080" alt="">
    <img src="https://picsum.photos/id/656/1280/720" alt="">
    <img src="https://picsum.photos/id/646/1366/768" alt="">
</div>
              
            
!

CSS

              
                #app {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

img {
    display: block;
    width: 33%;
    height: auto;
}
              
            
!

JS

              
                //関数定義
const myFunc = function(src){
    //Promiseオブジェクトを生成して返す
    return new Promise(function(resolve, reject){
        //Imageオブジェクトを生成
        const image = new Image();
        //読み込む画像を設定(関数の引数で取得した画像パスを代入)
        image.src = src;
        //onloadで画像読み込み完了後に処理
        image.onload = function(){
            //成功時にthenの処理へ
            resolve(image);
        }
        //onerrorで画像読み込みエラー時に処理
        image.onerror = function(error){
            //失敗時にcatchの処理へ
            reject(error);
        }
    });
}

//ページ内のimg要素を取得
const imgs = document.getElementsByTagName('img');

//img要素の数だけ繰り返し処理
for (const img of imgs) {
    //img要素のsrc属性の値を取得
    const src = img.getAttribute('src');
    //関数実行
    myFunc(src)
    //読み込みが完了した(画像が設定された)Imageオブジェクトを受け取って処理
    .then(function(res){
        //img要素のwidth属性に値を設定
        img.setAttribute('width', res.width);
        //img要素のheight属性に値を設定
        img.setAttribute('height', res.height);
    })
    //読み込みエラー時の処理
    .catch(function(error){
        console.log(error);
    });
}
              
            
!
999px

Console