办法一:应用reduce,includes
1.定义数组

let numArr = ['1','9','9','7','0','4','1','2','2','4','0']

2.封装一个去重办法 remove()

function remove(arr) {  return arr.reduce((newarr,cur) => {    if(newarr.includes(cur) === false) newarr.push(cur)    return newarr  },[])} 

3.执行去重办法
remove(numArr)

4.输入后果
['1','9','7','0','4','2']