update the master branch to the latest

src/components/back-top/back-top.vue

@@ -0,0 +1,81 @@
+<template>
+    <div :class="classes" :style="styles" @click="back">
+        <slot>
+            <div :class="innerClasses">
+                <i class="ivu-icon ivu-icon-ios-arrow-up"></i>
+            </div>
+        </slot>
+    </div>
+</template>
+<script>
+    import { scrollTop } from '../../utils/assist';
+    import { on, off } from '../../utils/dom';
+    const prefixCls = 'ivu-back-top';
+
+    export default {
+        props: {
+            height: {
+                type: Number,
+                default: 400
+            },
+            bottom: {
+                type: Number,
+                default: 30
+            },
+            right: {
+                type: Number,
+                default: 30
+            },
+            duration: {
+                type: Number,
+                default: 1000
+            }
+        },
+        data () {
+            return {
+                backTop: false
+            };
+        },
+        mounted () {
+//            window.addEventListener('scroll', this.handleScroll, false);
+//            window.addEventListener('resize', this.handleScroll, false);
+            on(window, 'scroll', this.handleScroll);
+            on(window, 'resize', this.handleScroll);
+        },
+        beforeDestroy () {
+//            window.removeEventListener('scroll', this.handleScroll, false);
+//            window.removeEventListener('resize', this.handleScroll, false);
+            off(window, 'scroll', this.handleScroll);
+            off(window, 'resize', this.handleScroll);
+        },
+        computed: {
+            classes () {
+                return [
+                    `${prefixCls}`,
+                    {
+                        [`${prefixCls}-show`]: this.backTop
+                    }
+                ];
+            },
+            styles () {
+                return {
+                    bottom: `${this.bottom}px`,
+                    right: `${this.right}px`
+                };
+            },
+            innerClasses () {
+                return `${prefixCls}-inner`;
+            }
+        },
+        methods: {
+            handleScroll () {
+                this.backTop = window.pageYOffset >= this.height;
+            },
+            back () {
+                const sTop = document.documentElement.scrollTop || document.body.scrollTop;
+                scrollTop(window, sTop, 0, this.duration);
+                this.$emit('on-click');
+            }
+        }
+    };
+</script>

src/components/back-top/index.js

@@ -0,0 +1,2 @@
+import BackTop from './back-top.vue';
+export default BackTop;