Vue JS-indexOf数组不是函数

Question

I'm trying to check if a number is present in an array (which I've done a thousand times before using .indexOf() ) but I seem to be missing something now.

Vue method

showSeat(seat) {
    if( !this.selectedSeats.length ) { 
        this.selectedSeats.push(seat)
    } else {
        let index = this.selectedSeats.indexOf(seat)
        ( index >= 0 ) ? this.selectedSeats.splice(index,1) : this.selectedSeats.push(seat)
    }
}

Initially, this.selectedSeats is equal to [] , and the first condition runs perfectly. However, when I try to add another seat , I get [Vue warn]: Error in event handler for "showSeat": "TypeError: this.selectedSeats.indexOf(...) is not a function" . What am I missing?

Answer 1

This is one of those rare cases in JavaScript where leaving off a semicolon can cause huge problems. These two lines are being evaluated as a single expression:

 let index = this.selectedSeats.indexOf(seat)
 ( index >= 0 ) ? this.selectedSeats.splice(index,1) : this.selectedSeats.push(seat)

It's trying to execute this.selectedSeats.indexOf(seat)(index>=0)

Add a semicolon at the end of your indexOf(seat); and you should be fine.