数组去重

let arr = [1,2,1,2,3,5,4,5,3,4,4,4,4];
let result = arr.sort().reduce((init, current)=>{
    if(init.length===0 || init[init.length-1]!==current){
        init.push(current);
    }
    return init;
}, []);
console.log(result); //[1,2,3,4,5]