diff --git a/client/pages/viewerpage/audioplayer.js b/client/pages/viewerpage/audioplayer.js
index 6d22a14d..340f85b0 100644
--- a/client/pages/viewerpage/audioplayer.js
+++ b/client/pages/viewerpage/audioplayer.js
@@ -1,25 +1,18 @@
-import React from "react";
+import React, { useState, useEffect, useLayoutEffect } from "react";
 import WaveSurfer from "wavesurfer.js";
 
 import { MenuBar } from "./menubar";
 import { NgIf, Icon } from "../../components/";
 import "./audioplayer.scss";
 
-export class AudioPlayer extends React.Component {
-    constructor(props) {
-        super(props);
-        this.state = {
-            wafesurfer: null,
-            loading: true,
-            isPlaying: true,
-            error: null,
-        };
-        this.toggle = this.toggle.bind(this);
-        window.addEventListener("keypress", this.toggle);
-    }
+export function AudioPlayer({ filename, data }) {
+    const [isPlaying, setIsPlaying] = useState(false);
+    const [isLoading, setIsLoading] = useState(true);
+    const [wavesurfer, setWavesurfer] = useState(null);
+    const [error, setError] = useState(null);
 
-    componentDidMount() {
-        const wavesurfer = WaveSurfer.create({
+    useLayoutEffect(() => {
+        const _ws = WaveSurfer.create({
             container: "#waveform",
             waveColor: "#323639",
             progressColor: "#6f6f6f",
@@ -28,81 +21,75 @@ export class AudioPlayer extends React.Component {
             height: 250,
             barWidth: 1,
         });
-        this.setState({ wavesurfer: wavesurfer });
-        wavesurfer.on("ready", () => {
-            this.setState({ loading: false });
-            if (this.state.isPlaying === true) {
-                wavesurfer.play();
-            }
+
+        _ws.on("ready", () => {
+            setIsLoading(false);
         });
-        wavesurfer.on("error", (err) => {
-            this.setState({ error: err, loading: false });
+        _ws.on("error", (err) => {
+            setIsLoading(false);
+            setError(err)
         });
-        wavesurfer.load(this.props.data);
-    }
+        _ws.load(data);
+        setWavesurfer(_ws);
+        return () => _ws.destroy();
+    }, []);
 
-    componentWillUnmount() {
-        if (this.state.wavesurfer) {
-            this.state.wavesurfer.destroy();
+    useEffect(() => {
+        if(wavesurfer === null) return;
+        window.addEventListener("keypress", onKeyPressHandler);
+        return () => window.removeEventListener("keypress", onKeyPressHandler);
+    }, [wavesurfer, isPlaying])
+
+    const onKeyPressHandler = (e) => {
+        if(e.code !== "Space") {
+            return
         }
-        window.removeEventListener("keypress", this.toggle);
-    }
+        isPlaying ? onPause(e) : onPlay(e);
+    };
 
-    toggle() {
-        if (this.state.isPlaying === true) {
-            this.setState({ isPlaying: false });
-            this.state.wavesurfer.pause();
-        } else {
-            this.setState({ isPlaying: true });
-            this.state.wavesurfer.play();
-        }
-    }
-
-    onPlay(e) {
+    const onPlay = (e) => {
         e.preventDefault();
         e.stopPropagation();
-        this.setState({ isPlaying: true });
-        this.state.wavesurfer.play();
+        wavesurfer.play();
+        setIsPlaying(true);
     }
 
-    onPause(e) {
+    const onPause = (e) => {
         e.preventDefault();
         e.stopPropagation();
-        this.setState({ isPlaying: false });
-        this.state.wavesurfer.pause();
+        wavesurfer.pause();
+        setIsPlaying(false);
     }
 
-    render() {
-        return (
-            <div className="component_audioplayer">
-                <MenuBar title={this.props.filename} download={this.props.data} />
-                <div className="audioplayer_container">
-                    <NgIf cond={this.state.error !== null} className="audioplayer_error">
-                        {this.state.error}
+    return (
+        <div className="component_audioplayer">
+            <MenuBar title={filename} download={data} />
+            <div className="audioplayer_container">
+                <NgIf cond={error !== null} className="audioplayer_error">
+                    {error}
+                </NgIf>
+                <NgIf cond={error === null}>
+                    <NgIf cond={isLoading === true}>
+                        <Icon name="loading" />
                     </NgIf>
-                    <NgIf cond={this.state.error === null}>
-                        <NgIf cond={this.state.loading === true}>
-                            <Icon name="loading" />
-                        </NgIf>
-                        <div className="audioplayer_box"
-                            style={{ opacity: this.state.loading? "0" : "1" }}>
-                            <div className="audioplayer_control">
-                                <NgIf cond={this.state.isPlaying === false}>
-                                    <span onClick={this.onPlay.bind(this)}>
-                                        <Icon name="play"/>
-                                    </span>
-                                </NgIf>
-                                <NgIf cond={this.state.isPlaying === true}>
-                                    <span onClick={this.onPause.bind(this)}>
-                                        <Icon name="pause"/>
-                                    </span>
-                                </NgIf>
-                            </div>
-                            <div id="waveform"></div>
+                    <div className="audioplayer_box"
+                         style={{ opacity: isLoading? "0" : "1" }}>
+                        <div className="audioplayer_control">
+                            <NgIf cond={isPlaying === false}>
+                                <span onClick={onPlay}>
+                                    <Icon name="play"/>
+                                </span>
+                            </NgIf>
+                            <NgIf cond={isPlaying === true}>
+                                <span onClick={onPause}>
+                                    <Icon name="pause"/>
+                                </span>
+                            </NgIf>
                         </div>
-                    </NgIf>
-                </div>
+                        <div id="waveform"></div>
+                    </div>
+                </NgIf>
             </div>
-        );
-    }
+        </div>
+    )
 }
diff --git a/client/pages/viewerpage/audioplayer.scss b/client/pages/viewerpage/audioplayer.scss
index 45998300..8693eb93 100644
--- a/client/pages/viewerpage/audioplayer.scss
+++ b/client/pages/viewerpage/audioplayer.scss
@@ -33,6 +33,7 @@
                 right: 10px;
                 z-index: 2;
                 height: 30px;
+                width: 30px;
 
                 > div {
                     display: inline;
diff --git a/client/pages/viewerpage/filedownloader.js b/client/pages/viewerpage/filedownloader.js
index c6dca52f..4f81ca6a 100644
--- a/client/pages/viewerpage/filedownloader.js
+++ b/client/pages/viewerpage/filedownloader.js
@@ -1,46 +1,38 @@
-import React from "react";
+import React, { useState, useEffect } from "react";
 
 import { NgIf, Icon } from "../../components/";
 import "./filedownloader.scss";
 import { t } from "../../locales/";
 
-export class FileDownloader extends React.Component {
-    constructor(props) {
-        super(props);
-        this.state = { loading: false, id: null };
-    }
-
-    onClick() {
+export function FileDownloader({ filename, data }) {
+    const [isDownloading, setIsDownloading] = useState(false);
+    const onClick = () => {
         document.cookie = "download=yes; path=/; max-age=60;";
-        this.setState({
-            loading: true,
-            id: window.setInterval(function() {
-                if (/download=yes/.test(document.cookie) === false) {
-                    this.setState({ loading: false });
-                    window.clearInterval(this.state.id);
-                }
-            }.bind(this), 80),
-        });
-    }
+        setIsDownloading(true);
+    };
 
-    componentWillUnmount() {
-        window.clearInterval(this.state.id);
-    }
+    useEffect(() => {
+        if(!isDownloading) return;
+        const t = setInterval(() => {
+            if (/download=yes/.test(document.cookie) === false) {
+                setIsDownloading(false);
+            }
+        }, 250);
+        return () => clearInterval(t);
+    }, [isDownloading]);
 
-    render() {
-        return (
-            <div className="component_filedownloader">
-                <div className="download_button">
-                    <a download={this.props.filename} href={this.props.data}>
-                        <NgIf onClick={this.onClick.bind(this)} cond={!this.state.loading}>
-                            { t("DOWNLOAD") }
-                        </NgIf>
-                    </a>
-                    <NgIf cond={this.state.loading}>
-                        <Icon name="loading"/>
+    return (
+        <div className="component_filedownloader">
+            <div className="download_button">
+                <a download={filename} href={data}>
+                    <NgIf onClick={onClick} cond={!isDownloading}>
+                        { t("DOWNLOAD") }
                     </NgIf>
-                </div>
+                </a>
+                <NgIf cond={isDownloading}>
+                    <Icon name="loading"/>
+                </NgIf>
             </div>
-        );
-    }
+        </div>
+    );
 }
diff --git a/client/pages/viewerpage/formviewer.js b/client/pages/viewerpage/formviewer.js
index b96d416f..77ace0a4 100644
--- a/client/pages/viewerpage/formviewer.js
+++ b/client/pages/viewerpage/formviewer.js
@@ -1,4 +1,4 @@
-import React from "react";
+import React, { useState } from "react";
 import ReactCSSTransitionGroup from "react-addons-css-transition-group";
 
 import { MenuBar } from "./menubar";
@@ -6,41 +6,25 @@ import { Container, FormBuilder, NgIf, Icon, Fab } from "../../components/";
 import { appendShareToUrl } from "../../helpers/";
 import "./formviewer.scss";
 
-export class FormViewer extends React.Component {
-    constructor(props) {
-        super(props);
-        this.state = {
-            form: {},
-        };
-    }
+export function FormViewer({
+    filename, data, content,
+    needSaving, isSaving, needSavingUpdate, onSave,
+}) {
+    const [form, setForm] = useState(JSON.parse(content));
 
-    componentDidMount() {
-        this.setState({
-            form: JSON.parse(this.props.content),
-        });
-    }
+    const onFormChange = () => {
+        JSON.stringify(form) === content ? needSavingUpdate(false) : needSavingUpdate(true);
+    };
 
-    onChange() {
-        this.setState({ refresh: Math.random() });
-        if (JSON.stringify(this.state.form) === this.props.content) {
-            this.props.needSavingUpdate(false);
-        } else {
-            this.props.needSavingUpdate(true);
-        }
-    }
-
-    save() {
-        if (this.props.needSaving === false) return;
+    const onClickSave = () => {
+        if (needSaving === false) return;
         const blob = new window.Blob([
-            JSON.stringify(this.state.form),
+            JSON.stringify(form),
         ], { type: "text/plain" });
+        return onSave(blob).then(() => needSavingUpdate(false));
+    };
 
-        return this.props
-            .onSave(blob)
-            .then(() => this.props.needSavingUpdate(false));
-    }
-
-    simpleMarkdown(text) {
+    const simpleMarkdown = (text) => {
         const regLink = /\[([^\]]*)\]\(([^\)]+)\)/g;
         return text
             .replace(regLink, function(str) {
@@ -50,9 +34,9 @@ export class FormViewer extends React.Component {
             })
             .replace(regLink, "<a href=\"$2\">$1</a>")
             .replace(/\n/g, "<br>");
-    }
+    };
 
-    beautify(label) {
+    const beautify = (label) => {
         return label
             .split("_")
             .map((t) => {
@@ -61,78 +45,77 @@ export class FormViewer extends React.Component {
                 return t[0].toUpperCase() + t.substring(1);
             })
             .join(" ");
-    }
+    };
 
-    render() {
-        const renderForm = ($input, props, struct, onChange) => {
-            return (
-                <label className={"no-select"}>
-                    <div>
-                        <span>
-                            {
-                                this.beautify(struct.label)
-                            }<span className="mandatory">{struct.required ? "*" : ""}</span>
-                        </span>
-                        <div style={{ width: "100%" }}>
-                            { $input }
-                        </div>
-                    </div>
-                    <div>
-                        <span className="nothing"></span>
-                        <div style={{ width: "100%" }}>
-                            {
-                                struct.description ? (
-                                    <div
-                                        className="description"
-                                        dangerouslySetInnerHTML={{
-                                            __html: this.simpleMarkdown(struct.description),
-                                        }}
-                                    />
-                                ) : null
-                            }
-                        </div>
-                    </div>
-                </label>
-            );
-        };
+    const renderForm = ($input, props, struct, onChange) => {
         return (
-            <div className="component_formviewer">
-                <MenuBar title={this.props.filename} download={this.props.data} />
-                <div className="formviewer_container">
-                    <Container>
-                        <form className="sticky box">
-                            <FormBuilder
-                                form={this.state.form}
-                                onChange={this.onChange.bind(this)}
-                                render={renderForm}
-                            />
-                        </form>
-                    </Container>
-                    <ReactCSSTransitionGroup
-                        transitionName="fab" transitionLeave={true} transitionEnter={true}
-                        transitionAppear={true} transitionAppearTimeout={400}
-                        transitionEnterTimeout={400} transitionLeaveTimeout={200}>
-                        <NgIf key={this.props.needSaving} cond={this.props.needSaving}>
-                            <NgIf cond={!this.props.isSaving}>
-                                <Fab onClick={this.save.bind(this)}>
-                                    <Icon
-                                        name="save"
-                                        style={{ height: "100%", width: "100%" }}
-                                    />
-                                </Fab>
-                            </NgIf>
-                            <NgIf cond={this.props.isSaving}>
-                                <Fab>
-                                    <Icon
-                                        name="loading"
-                                        style={{ height: "100%", width: "100%" }}
-                                    />
-                                </Fab>
-                            </NgIf>
-                        </NgIf>
-                    </ReactCSSTransitionGroup>
+            <label className={"no-select"}>
+                <div>
+                    <span>
+                        {
+                            beautify(struct.label)
+                        }<span className="mandatory">{struct.required ? "*" : ""}</span>
+                    </span>
+                    <div style={{ width: "100%" }}>
+                        { $input }
+                    </div>
                 </div>
-            </div>
+                <div>
+                    <span className="nothing"></span>
+                    <div style={{ width: "100%" }}>
+                        {
+                            struct.description ? (
+                                <div
+                                    className="description"
+                                    dangerouslySetInnerHTML={{
+                                        __html: simpleMarkdown(struct.description),
+                                    }}
+                                />
+                            ) : null
+                        }
+                    </div>
+                </div>
+            </label>
         );
-    }
+    };
+
+    return (
+        <div className="component_formviewer">
+            <MenuBar title={filename} download={data} />
+            <div className="formviewer_container">
+                <Container>
+                    <form className="sticky box">
+                        <FormBuilder
+                            form={form}
+                            onChange={onFormChange}
+                            render={renderForm}
+                        />
+                    </form>
+                </Container>
+                <ReactCSSTransitionGroup
+                    transitionName="fab" transitionLeave={true} transitionEnter={true}
+                    transitionAppear={true} transitionAppearTimeout={400}
+                    transitionEnterTimeout={400} transitionLeaveTimeout={200}>
+                    <NgIf key={needSaving} cond={needSaving}>
+                        <NgIf cond={!isSaving}>
+                            <Fab onClick={onClickSave}>
+                                <Icon
+                                    name="save"
+                                    style={{ height: "100%", width: "100%" }}
+                                />
+                            </Fab>
+                        </NgIf>
+                        <NgIf cond={isSaving}>
+                            <Fab>
+                                <Icon
+                                    name="loading"
+                                    style={{ height: "100%", width: "100%" }}
+                                />
+                            </Fab>
+                        </NgIf>
+                    </NgIf>
+                </ReactCSSTransitionGroup>
+            </div>
+        </div>
+    );
 }
diff --git a/client/pages/viewerpage/pdfviewer.js b/client/pages/viewerpage/pdfviewer.js
index 31463b2e..91701a01 100644
--- a/client/pages/viewerpage/pdfviewer.js
+++ b/client/pages/viewerpage/pdfviewer.js
@@ -9,20 +9,22 @@ const PDFJSViewer = (props) => (
     </Bundle>
 );
 
-
-export const PDFViewer = ({ data, filename }) => {
-    const ViewerComponent = "application/pdf" in navigator.mimeTypes ?
-        <embed
-            src={`${data}#toolbar=0`}
-            type="application/pdf"
-            style={{ height: "100%", width: "100%" }}>
-        </embed> : <PDFJSViewer src={data} />;
-
+export function PDFViewer({ filename, data }) {
     return (
         <div className="component_pdfviewer">
             <MenuBar title={filename} download={data} />
             <div className="pdfviewer_container">
-                { ViewerComponent }
+                {
+                    "application/pdf" in navigator.mimeTypes ? (
+                        <embed
+                            src={`${data}#toolbar=0`}
+                            type="application/pdf"
+                            style={{ height: "100%", width: "100%" }}>
+                        </embed>
+                    ) : (
+                        <PDFJSViewer src={data} />
+                    )
+                }
             </div>
         </div>
     );