双层for循环 数组简单去重

let arr = [1, 3, 5, 1, 7, 9, 9]
for (let i = 0; i < arr.length; i++) {
    for (let j = i + 1; j < arr.length; j++) {
        if (arr[i] == arr[j]) {
            arr.splice(i, 1)
        }
    }
}
console.log('arr: ', arr) // [3, 5, 1, 7, 9]