数组去重indexOf、Set、include

var arr = [1, 2, 3, 3, 4, 5, 6, 6, 7, 8, 9];

indexOf去重

var newList = [];
for (var i = 0; i < arr.length; i++) {
  if (newList.indexOf(arr[i]) === -1) {
    newList.push(arr[i])
  }
}

Set去重

let setList = new Set(arr);
let newList1 = [...setList]

include去重

var newList2 = [];
for (var i = 0; i < arr.length; i++) {
  if (!newList2.includes(arr[i])) {
    newList2.push(arr[i])
  }
}

测试

console.log(newList,newList1,newList2);//[ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],[ 1, 2, 3, 4, 5, 6, 7, 8, 9 ],[ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]