Javascript 交换React.js中的元素并获取<;错误>;
所以我有一副学习卡,上面有一个链接可以开始学习。用户完成学习会话后,我不希望用户在两分钟内访问学习会话链接。我没有使用链接,而是使用timeLeft状态使用计时器从2分钟倒计时到0分钟。2分钟后,计时器消失,并通过在componentDidUpdate中将状态设置为“link”来替换为研究会话的链接。一切都按预期工作,除了react会减慢deck页面的呈现速度。我的代码如下:Javascript 交换React.js中的元素并获取<;错误>;,javascript,backbone.js,reactjs,Javascript,Backbone.js,Reactjs,所以我有一副学习卡,上面有一个链接可以开始学习。用户完成学习会话后,我不希望用户在两分钟内访问学习会话链接。我没有使用链接,而是使用timeLeft状态使用计时器从2分钟倒计时到0分钟。2分钟后,计时器消失,并通过在componentDidUpdate中将状态设置为“link”来替换为研究会话的链接。一切都按预期工作,除了react会减慢deck页面的呈现速度。我的代码如下: /** @jsx React.DOM */ var cardModel = require("../models/car
/** @jsx React.DOM */
var cardModel = require("../models/card.js");
var Card = React.createFactory(require("./card.jsx"));
//var BackboneMixin = require("../../BackboneMixin.js");
var DeckShow = React.createClass({
//mixins: [BackboneMixin],
getInitialState: function() {
return {elapsedTime: this.setTime(), timeLeft: 0, cards: this.props.cards, cardsCollection: [], cardShow: "question", empty: "none" }
},
componentDidMount: function () {
this.props.cardCollection.fetch();
var boxes = this.getBoxState(this.props.deck)
this.setState({timeLeft: this.props.delay - this.state.elapsedTime})
this.interval = setInterval(this.countDown, 1000)
var startBox = [];
var i = 0;
while (i <= (this.props.deck.get("session_num") % 5)) {
startBox.concat(boxes[i])
i += 1;
}
if ((this.props.deck.get("cards").length > 0) && (this.state.elapsedTime >= this.props.delay || this.props.deck.get("last_session") === null)) {
this.setState({empty: "link"});
} else if (this.props.deck.get("cards").length > 0 && startBox.length === 0) {
this.setState({empty: "timer"})
//setTimeout(this.setState({empty: "link"}), this.state.timeLeft)
}
else{
this.setState({empty: "none"});
}
},
componentDidUpdate: function(nextProps, nextState) {
this.props.deck.on("sync", function(){
this.forceUpdate();
}, this)
if (this.state.timeLeft <= 0) {
clearInterval(this.interval)
this.setState({empty: "link"})
this.forceUpdate();
}
},
componentWillUpdate: function(){
// var that = this;
// if (this.state.elapsedTime <= 0) {
// that.setState({empty: that.link})
// }
},
componentWillUnmount: function(){
clearInterval(this.interval);
},
setTime: function(){
var last = this.props.deck.get("last_session") || Date.now();
return Date.now() - last;
},
getBoxState: function(deck) {
var boxState = [[],[],[],[],[]]
var deckCards = deck.get("cards");
for (var i = 0; i < deckCards.length; i++) {
boxState[deckCards[i].box_id].push(deckCards[i])
}
return boxState;
},
countDown: function() {
this.setState({timeLeft: this.state.timeLeft - 1000})
},
handleSubmit: function(event) {
event.preventDefault();
var question = this.refs.question.getDOMNode().value.trim();
var answer = this.refs.answer.getDOMNode().value.trim();
if ((!question) || (!answer)) {
return;
}
this.refs.question.getDOMNode().value = '';
this.refs.answer.getDOMNode().value = '';
var cards = this.props.cardCollection.models[0].get("objects")
var newCard = {
question: question,
answer: answer,
deck_id: this.props.id,
box_id: 0
}
this.props.cardCollection.create(newCard, {wait: true})
var cardArr = this.state.cards
cardArr.push(newCard)
this.setState({empty: "link"});
this.setState({cards: cardArr})
return;
},
render: function() {
var header = "Deck: " + this.props.deck.get("name");
var cardsList = this.props.cards.map(function(card) {
return <Card box={card.box_id}
key={card.id}
cardQuestion={card.question}
cardAnswer={card.answer}
text={card.answer} />
});
var view;
var empty = this.state.empty;
var that = this;
var elapsed = this.state.timeLeft;
var none = <p>{"There are no cards"}</p>
var timer = <p>{"Time till next: " + Math.floor(elapsed/60000) + ":" + Math.floor((elapsed % 60000)/1000)}</p>
var link = <a href={"#/decks/" + this.props.id + "/study"}>{"Study Mode"}</a>
if (this.state.empty === "link") {
view = link;
} else if (this.state.empty === "timer") {
view = timer;
} else {
view = none;
}
return (
<div className="cardList">
<h2>{header}</h2>
<div id="study-mode">
{view}
</div>
<ul id="deck-index">{cardsList}</ul>
<div className="input">
<form onSubmit={this.handleSubmit} className="form-horizontal">
<div className="form-group">
<input
type="text"
ref="question"
placeholder="Add a new question" />
<br />
<input
type="textarea"
ref="answer"
placeholder="Add an answer" />
<br />
<input type="submit" value="Add Card" />
</div>
</form>
</div>
</div>
);
}
});
module.exports = DeckShow;
/**@jsx React.DOM*/
var cardModel=require(“../models/card.js”);
var Card=React.createFactory(需要(“./Card.jsx”);
//var BackboneMixin=require(“../../BackboneMixin.js”);
var DeckShow=React.createClass({
//mixin:[BackboneMixin],
getInitialState:函数(){
return{elapsedTime:this.setTime(),timeLeft:0,cards:this.props.cards,cardsCollection:[],cardsShow:“问题”,空:“无”}
},
componentDidMount:函数(){
this.props.cardCollection.fetch();
var-box=this.getBoxState(this.props.deck)
this.setState({timeLeft:this.props.delay-this.state.elapsedTime})
this.interval=setInterval(this.countDown,1000)
var startBox=[];
var i=0;
而(i 0)和(this.state.elapsedTime>=this.props.delay | | | this.props.deck.get(“上次会话”)==null)){
this.setState({empty:“link”});
}else if(this.props.deck.get(“cards”).length>0&&startBox.length==0){
this.setState({empty:“timer”})
//setTimeout(this.setState({empty:“link”}),this.state.timeLeft)
}
否则{
this.setState({empty:“none”});
}
},
componentDidUpdate:函数(nextProps,nextState){
this.props.deck.on(“sync”,function()){
这个.forceUpdate();
},本页)
如果(this.state.timeLeft调用this.forceUpdate()
在componentdiddupdate
内部导致代码中无限递归。每当组件的属性或状态更改时以及forceUpdate()时,都会调用componentdiddupdate
update方法调用了
。因此您将得到componentDidUpdate->forceUpdate->componentDidUpdate->forceUpdate->……[无限递归]
要解决此问题,请执行以下操作:
将this.props.deck
订阅从componentDidUpdate
移动到componentDidMount
。该订阅只需在安装组件时添加,而不是每次更新任何内容时添加
从componentDidUpdate