问setInterval返回未定义的或返回值的范围错误

EN

class Signal {
    t : number;
    private intervallId : number | undefined;
    
    
    constructor(t : number) {
        this.t = t;
              
    }

    wait() {
        
        this.intervallId = setInterval(this.signalTriggered, this.t)
        console.log("Never executed.")
    }

    signalTriggered() {
        const triggerTime : number = Date.now()
        console.log(this.intervallId) /* always undefined */
        if (this.intervallId) {clearInterval(this.intervallId)
        console.log(triggerTime); }
    }
}

var timer = new Signal(2000)
    timer.wait()
    console.log("Done.") /* Never printed out. */