Header component

2 files changed, 71 insertions, 63 deletions

diff --git a/vnext/src/components/Header.js b/vnext/src/components/Header.js
new file mode 100644
index 00000000..fd1c1705
--- /dev/null
+++ b/vnext/src/components/Header.js
@@ -0,0 +1,67 @@
+import React from 'react';
+
+const elClassHidden = 'header--hidden'
+const elClassBackground = 'header--background';
+
+export default class Header extends React.Component {
+    constructor(props) {
+        super(props);
+        this.dHeight = 0;
+        this.wHeight = 0;
+        this.wScrollCurrent = 0;
+        this.wScrollBefore = 0;
+        this.wScrollDiff = 0;
+        this.header = React.createRef()
+    }
+    componentDidMount() {
+        const header = this.header.current;
+        window.addEventListener('scroll', this.throttle(250, () => {
+            this.dHeight = document.body.offsetHeight;
+            this.wHeight = window.innerHeight;
+            this.wScrollCurrent = window.pageYOffset;
+            this.wScrollDiff = this.wScrollBefore - this.wScrollCurrent;
+
+            if (this.wScrollCurrent <= 0) {
+                // scrolled to the very top; element sticks to the top
+                header.classList.remove(elClassHidden)
+                header.classList.remove(elClassBackground)
+            } else if (this.wScrollDiff > 0 && header.classList.contains(elClassHidden)) {
+                // scrolled up; element slides in
+                header.classList.remove(elClassHidden)
+                header.classList.add(elClassBackground)
+            } else if (this.wScrollDiff < 0) {
+                // scrolled down
+                if (this.wScrollCurrent + this.wHeight >= this.dHeight && header.classList.contains(elClassHidden)) {
+                    // scrolled to the very bottom; element slides in
+                    header.classList.remove(elClassHidden)
+                    header.classList.add(elClassBackground)
+                } else {
+                    // scrolled down; element slides out
+                    header.classList.add(elClassHidden)
+                }
+            }
+            this.wScrollBefore = this.wScrollCurrent;
+        }), { passive: true });
+    }
+    throttle(delay, fn) {
+        var last, deferTimer;
+        return function () {
+            var context = this, args = arguments, now = +new Date;
+            if (last && now < last + delay) {
+                clearTimeout(deferTimer);
+                deferTimer = setTimeout(
+                    function () {
+                        last = now;
+                        fn.apply(context, args);
+                    },
+                    delay);
+            } else {
+                last = now;
+                fn.apply(context, args);
+            }
+        };
+    };
+    render() {
+        return (<header ref={this.header}>{this.props.children}</header>);
+    }
+}
\ No newline at end of file
diff --git a/vnext/src/index.js b/vnext/src/index.js
index 2caaf5bb..aeb5357f 100644
--- a/vnext/src/index.js
+++ b/vnext/src/index.js
@@ -13,9 +13,7 @@ import Thread from './components/Thread';
 import LoginButton from './components/LoginButton';
 import Footer from './components/Footer';
 import Avatar from './components/Avatar';
-
-const elClassHidden = 'header--hidden'
-const elClassBackground = 'header--background';
+import Header from './components/Header';
 
 class App extends React.Component {
   constructor(props) {
@@ -29,75 +27,18 @@ class App extends React.Component {
       visitor: {
         uid: Number(window.localStorage.uid) || 0,
         hash: window.localStorage.hash || params.hash || ''
-      },
-      headerClassName: ''
+      }
     };
-    this.dHeight = 0;
-    this.wHeight = 0;
-    this.wScrollCurrent = 0;
-    this.wScrollBefore = 0;
-    this.wScrollDiff = 0;
   }
-
   componentDidMount() {
-    window.addEventListener('scroll', this.throttle(500, () => {
-      this.dHeight = document.body.offsetHeight;
-      this.wHeight = window.innerHeight;
-      this.wScrollCurrent = window.pageYOffset;
-      this.wScrollDiff = this.wScrollBefore - this.wScrollCurrent;
-
-      if (this.wScrollCurrent <= 0) {
-        // scrolled to the very top; element sticks to the top
-        this.setState({
-          headerClassName: ''
-        })
-      } else if (this.wScrollDiff > 0 && this.state.headerClassName.indexOf(elClassHidden) >= 0) {
-        // scrolled up; element slides in
-        this.setState({
-          headerClassName: elClassBackground
-        })
-      } else if (this.wScrollDiff < 0) {
-        // scrolled down
-        if (this.wScrollCurrent + this.wHeight >= this.dHeight && this.state.headerClassName.indexOf(elClassHidden) >= 0) {
-          // scrolled to the very bottom; element slides in
-          this.setState({
-            headerClassName: elClassBackground
-          })
-        } else {
-          // scrolled down; element slides out
-          this.setState({
-            headerClassName: [elClassHidden, elClassBackground].join(' ')
-          })
-        }
-      }
-      this.wScrollBefore = this.wScrollCurrent;
-    }));
     this.auth(this.state.visitor.hash)
   }
-  throttle(delay, fn) {
-    var last, deferTimer;
-    return function () {
-      var context = this, args = arguments, now = +new Date;
-      if (last && now < last + delay) {
-        clearTimeout(deferTimer);
-        deferTimer = setTimeout(
-          function () {
-            last = now;
-            fn.apply(context, args);
-          },
-          delay);
-      } else {
-        last = now;
-        fn.apply(context, args);
-      }
-    };
-  };
   render() {
     const user = this.state.visitor;
     return (
       <Router>
         <React.Fragment>
-          <header className={this.state.headerClassName}>
+          <Header>
             <div id="header_wrapper">
               {user.uid > 0 ?
                 <div id="ctitle">
@@ -130,7 +71,7 @@ class App extends React.Component {
                 </ul>
               </nav>
             </div>
-          </header>
+          </Header>
           <div id="wrapper">
             <section id="content">
               <Switch>