Method constructor

lib/eta.js:5–15

(length, initTime, initValue)

class ETA{

    constructor(length, initTime, initValue){
        // size of eta buffer
        this.etaBufferLength = length || 100;

        // eta buffer with initial values
        this.valueBuffer = [initValue];
        this.timeBuffer = [initTime];

        // eta time value
        this.eta = '0';
    }

    // add new values to calculation buffer
    update(time, value, total){