Add some calculated data to onscroll params.

Author: tangbc

README.md

@@ -77,7 +77,7 @@ npm install vue-virtual-scroll-list --save
 </script>
 ```
 
-The `<Item>` component is included inside but defined outside the `<virtualList>` component. We see that `<virtualList>` does **not** rely on the `<Item>` component. So you can use virtual-list with any component freely.
+The `<Item>` component is included inside but defined outside the `<virtualList>` component, we see that `<virtualList>` does **not** rely on the `<Item>` component, so you can use virtual-list with any component freely.
 
 #### Using by script include:
 
@@ -120,15 +120,15 @@ new Vue({
 :--- | :--- | :--- | :--- |
 | size | Number | ✓ | Each list item height, in variable height mode, this prop just use to calculate the virtual-list viewport height. |
 | remain | Number | ✓ | How many items should be shown in virtual-list viewport, so `size` and `remain` determine the outside container viewport height (size × remian). |
-| bench | Number | * | Default value is equal to `remain`, unreached items count, not show in virtual-list viewport but exist in real DOM, the larger the bench, the higher the scroll performance will achieved.  |
 | start | Number | * | Default value is `0`, the initial scroll start index. It must be integer and in the range of list index, if out of range it will be turned to `0` or the last one.  |
+| bench | Number | * | Default value is equal to `remain`, unreached items count, not show in virtual-list viewport but exist in real DOM, the larger the bench, the higher the scroll performance will achieved.  |
 | debounce | Number | * | **It's disabled by default**, milliseconds of using `debounce` function to ensure scroll event doesn't fire so often that it bricks browser performance. |
 | rtag | String | * | Default value is `div`, the virtual-list root element tag name, in all cases it's style is set to `display: block;` |
 | wtag | String | * | Default value is `div`, the virtual-list item wrapper element tag name, in all cases it's style is set to `display: block;` |
 | wclass | String | * | Default value is an empty string, the virtual-list item wrapper element class, has the same API with [`v-bind:class`](https://vuejs.org/v2/guide/class-and-style.html) |
-| onscroll | Function | * | Called when virtual-list scroll event handling, param: `(e, offset)`. |
 | totop | Function | * | Called when virtual-list is scrolled to top, no param. |
 | tobottom | Function | * | Called when virtual-list is scrolled to bottom, no param. |
+| onscroll | Function | * | Called when virtual-list is scrolling, param: `(e, { offset, offsetAll, start, end })`. |
 | variable | Function | * | For using virtual-list with variable height mode, this prop is a variable height getter function which is called with param: `(index)` when each item is ready to be calculated. |
 
 ### About variable height
@@ -138,7 +138,7 @@ In variable height mode, prop `size` is still required. All the index variable h
 
 ## Contributions
 
-Welcome to improve vue-virtual-scroll-list by any pull request or issue.
+Welcome to improve vue-virtual-scroll-list with any issue, pull request or code review.
 
 
 ## Changelogs

index.js

@@ -88,31 +88,34 @@
                 var delta = this.delta
                 var offset = this.$refs.vsl.scrollTop
 
-                if (!offset && delta.total) {
-                    this.triggerEvent('totop')
-                }
-
                 if (delta.total > delta.keeps) {
                     this.updateZone(offset)
                 }
 
-                if (offset >= delta.offsetAll) {
-                    this.triggerEvent('tobottom')
+                var offsetAll = delta.offsetAll
+                if (this.onscroll) {
+                    this.onscroll(e, {
+                        offset: offset,
+                        offsetAll: offsetAll,
+                        start: delta.start,
+                        end: delta.end
+                    })
                 }
 
-                if (this.onscroll) {
-                    this.onscroll(e, offset)
+                if (!offset && delta.total) {
+                    this.triggerEvent('totop')
+                }
+
+                if (offset >= offsetAll) {
+                    this.triggerEvent('tobottom')
                 }
             },
 
             // update render zone by scroll offset.
             updateZone: function (offset) {
-                var overs
-                if (this.variable) {
-                    overs = this.getVarOvers(offset)
-                } else {
-                    overs = Math.floor(offset / this.size)
-                }
+                var overs = this.variable
+                    ? this.getVarOvers(offset)
+                    : Math.floor(offset / this.size)
 
                 var delta = this.delta
                 var zone = this.getZone(overs)
@@ -230,7 +233,7 @@
                 var delta = this.delta
 
                 index = parseInt(index, 10)
-                index = index < 0 ? 0 : index
+                index = Math.max(0, index)
 
                 var lastStart = delta.total - delta.keeps
                 var isLast = (index <= delta.total && index >= lastStart) || (index > delta.total)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "vue-virtual-scroll-list",
-  "version": "1.1.6",
+  "version": "1.1.7",
   "description": "A vue (2.x) component that support big data and infinite loading by using virtual scroll list.",
   "main": "index.js",
   "files": [