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node_modules/vant/lib/tabs/utils.js

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+"use strict";
+
+exports.__esModule = true;
+exports.scrollLeftTo = scrollLeftTo;
+exports.scrollTopTo = scrollTopTo;
+
+var _raf = require("../utils/dom/raf");
+
+var _scroll = require("../utils/dom/scroll");
+
+function scrollLeftTo(scroller, to, duration) {
+  var count = 0;
+  var from = scroller.scrollLeft;
+  var frames = duration === 0 ? 1 : Math.round(duration * 1000 / 16);
+
+  function animate() {
+    scroller.scrollLeft += (to - from) / frames;
+
+    if (++count < frames) {
+      (0, _raf.raf)(animate);
+    }
+  }
+
+  animate();
+}
+
+function scrollTopTo(scroller, to, duration, callback) {
+  var current = (0, _scroll.getScrollTop)(scroller);
+  var isDown = current < to;
+  var frames = duration === 0 ? 1 : Math.round(duration * 1000 / 16);
+  var step = (to - current) / frames;
+
+  function animate() {
+    current += step;
+
+    if (isDown && current > to || !isDown && current < to) {
+      current = to;
+    }
+
+    (0, _scroll.setScrollTop)(scroller, current);
+
+    if (isDown && current < to || !isDown && current > to) {
+      (0, _raf.raf)(animate);
+    } else if (callback) {
+      (0, _raf.raf)(callback);
+    }
+  }
+
+  animate();
+}