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']