VUE 判斷數組中是否存在某個值

let barginFlag=[1,2,3,4];
let a=3;
let b=9;

//存在，flag1==0
let flag1= barginFlag.findIndex(item => item=== a)
console.log(flag1)

//不存在：flag2==-1
let flag2= barginFlag.findIndex(item => item=== b)
console.log(flag2)