优化textarea组件

src/form/textarea.js

@@ -18,6 +18,8 @@ class TextArea extends Component {
     readOnly: false,
     disabled: false,
     autosize: false,
+    maxheight: null,
+    minheight: null,
     maxlength: null,
     minlength: null,
     'show-limit': false,
@@ -157,11 +159,24 @@ class TextArea extends Component {
   onInput(e) {
     this.value = e.target.value
     if (this.autosize) {
-      nextTick(() => {
-        this.$refs.textarea.style.height = 'auto'
-        let height = this.$refs.textarea.scrollHeight + 'px'
-        this.$refs.textarea.style.height = height
-      })
+      nextTick(() => this.adjustTextareaSize())
+    }
+  }
+  adjustTextareaSize() {
+    let { maxheight, minheight } = this
+    const input = this.$refs.textarea
+    input.style.height = 'auto'
+    let height = input.scrollHeight
+
+    if (minheight && !Number.isNaN(+minheight)) {
+      height = Math.max(minheight, height)
+    }
+    if (maxheight && !Number.isNaN(+maxheight)) {
+      input.style.overflow = height > maxheight ? 'auto' : 'hidden'
+      height = Math.min(maxheight, height)
+    }
+    if (input.style.height !== height) {
+      input.style.height = height + 'px'
     }
   }
   onKeydown(ev) {
@@ -223,6 +238,10 @@ class TextArea extends Component {
       // 火狐浏览器需要手动focus()才能聚焦成功
       nextTick(_ => this.$refs.textarea.focus())
     }
+    if (this.autosize) {
+      this.minheight = this.minheight || this.offsetHeight - 2
+      this.adjustTextareaSize()
+    }
   }
 }