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19 lines
814 B
JavaScript
19 lines
814 B
JavaScript
async function createStreamVisualizer(asyncIterable,options){
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const{maxPoints,alpha,width,height,yDomain}=options;
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const{scaleLinear:sl,line}=await import('https://cdn.skypack.dev/d3');
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let points=[];
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let prevEma=NaN;
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for await(const{timestamp,value}of asyncIterable){
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const ema=isNaN(prevEma)?value:alpha*value+(1-alpha)*prevEma;
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points.push({timestamp,value,ema});
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prevEma=ema;
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if(points.length>maxPoints)points.shift();
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}
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if(!points.length)return{data:[],path:''};
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const xDomain=[points[0].timestamp,points[points.length-1].timestamp];
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const x=sl().domain(xDomain).range([0,width]);
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const y=sl().domain(yDomain).range([height,0]);
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const lineGen=line().x(d=>x(d.timestamp)).y(d=>y(d.ema));
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return{data:points,path:lineGen(points)};
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}
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export default createStreamVisualizer; |