Array.prototype.myFind = function(fn) {
for(let i=0;i<this.length;i++) {
if(fn(this[i])) return this[i]
}
}
let arr = [1,2,3,4,5,6]
let targetNum = arr.myFind((item)=>{
if(item>3){
return item
}
})
console.log('查詢結果', targetNum)
4