setTimeout（）如何访问聚合物元素的成员
setTimeout（）如何访问聚合物元素的成员
提问于 2019-03-26 04:29:34
这个问题在这里已有答案：
- 循环中的JavaScript闭包 - 简单实用的例子 39答案
我无法访问我的聚合物'类'的'成员'
Polymer({
is: 'sound-propagation',
time1: 0,
time2: 0,
timeDifference: 0,
timeCounter:0,
speed: 5,
distance: 5,
frequency: [],
amplitude: 15,
deflection: [],
animation: 0,
timeout: 0,
counter: 0,
appletStart: function(context, firstStart) {
this.initializeCircles();
this.changeFrequency(0.5);
this.setAnimation();
},
setAnimation: function(){
var self = this;
var timeout = setTimeout(function(){ console.log("frequencybla: "+self.frequency[6]);}, 3000);
this.animation = setInterval(function(){
if(self.counter >= 20){
self.time2 = Date.now();
self.timeDifference = (self.time2 - self.time1)/20000;
self.time1 = Date.now();
self.counter = 0;
}
for(var i = 0; i <=19; i+=1){
self.deflection[i] = self.amplitude*Math.sin(self.timeCounter*self.frequency[i]*2*Math.PI);
//console.log("deflection: "+self.deflection[i]);
//console.log("amplitude: "+self.amplitude);
//console.log("timeCounter: "+self.timeCounter);
//console.log("frequency: "+self.frequency[i]);
}
self.timeCounter += self.timeDifference;
self.counter += 1;
}, 1);
},
changeFrequency: function(newFrequency){
var self = this;
for(var i = 0; i <=19; i+=1){
//var timeout = setTimeout(function(){ self.setFrequency(i, newFrequency); console.log("frequencyTimeOut: "+self.frequency[i]);}, (this.distance/this.speed)*1*(i+1));
//this.setFrequency(i, newFrequency);
var timeout = setTimeout(function(){var j = i; self.frequency[j]=newFrequency; console.log("frequencyTimeOut: "+self.frequency[i]);}, 1000);
}
}
我正在尝试在超时函数内设置最外层频率数组的值，并在动画间隔内访问此值。但似乎值没有存储在正确的数组中，当我打印出控制台中的值时，它是未定义的。有人可以解释一下如何在我的超时功能中指定正确的数组吗？
我遗漏了一些代码，因为我觉得它并不重要。
回答 1
Stack Overflow用户
发布于 2019-03-26 13:31:59
在Polymer 2和3中，您可以使用箭头函数来确保this正确绑定setTimeout()。例如，这是Polymer 3中的一个简单时钟：
<html>
<body>
<script type="module">
import { PolymerElement, html } from 'https://unpkg.com/@polymer/polymer/polymer-element.js?module'
class MyClock extends PolymerElement {
static get properties () { return {clock: String} }
ready () {
super.ready()
this.updateClock()
}
updateClock () {
this.clock = new Date().toLocaleTimeString()
setTimeout(() => this.updateClock(), 1000)
}
static get template () { return html`Current time: [[clock]]` }
}
customElements.define('my-clock', MyClock)
</script>
<my-clock></my-clock>
</body>
</html>
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/-100005165
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