captain-ui/es/scroll/src/directive/load.js

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var count = 0;

function loadImg(el, url) {
  var img = new Image(); // eslint-disable-line

  var setUrl = function setUrl(imgUrl) {
    if (el.tagName.toLowerCase() === 'img') {
      el.setAttribute('src', imgUrl);
    } else {
      el.style.backgroundImage = "url(" + imgUrl + ")";
    }
  };

  return new Promise(function (r) {
    img.onload = function () {
      setUrl(url);
      r();
    };

    img.onerror = function () {
      setUrl();
      r('https://img.yzcdn.cn/upload_files/no_pic.png');
    };

    img.src = url;
  });
}

export default {
  bind: function bind(el, binding) {
    var target = el.querySelector('div[data-src]');
    var imgUrl = target.dataset.src;
    loadImg(target, imgUrl).then(function () {
      count++;
      binding.value(count);
    });
  }
};