數組去重

數組去重的幾種方法。

// es6  new Set();
// ES6 提供了新的數據結構 Set。它相似於數組，可是成員的值都是惟一的，沒有重複的值。
// Set自己是一個構造函數，用來生成 Set 數據結構。
let arr1 = [1,3,3,2,2,1,3];
function uniq1(arr){
    if (arr.length <= 1) { return arr; }
    return [...new Set(arr)].sort(function(a,b){
        return a - b;
    });
}
console.log(uniq1(arr1));   //[1, 2, 3]

// includes
let arr2 = [1,4,3,3,4,2,1,2,4];
function uniq2(arr){
    if (arr.length <= 1) { return arr; }
    let result = [];
    for(let i = 0;i<arr.length;i++){
        if(!result.includes(arr[i])){
            result.push(arr[i]);
        }
    }
    result.sort(function(a,b){
        return a-b;
    });
    return result;
}
console.log(uniq2(arr2));   //[1, 2, 3, 4]

// indexOf
let arr3 = [1,4,3,3,4,5,1,2,4,5,5];
function uniq3(arr){
    if (arr.length <= 1) { return arr; }
    let result = [];
    for(let i = 0;i<arr.length;i++){
        if(result.indexOf(arr[i]) === -1){
            result.push(arr[i]);
        }
    }
    result.sort(function(a,b){
        return a-b;
    });
    return result;
}
console.log(uniq3(arr3));   //[1, 2, 3, 4, 5]

// reduce
let arr4 = [1,4,3,6,4,5,1,2,4,5,5,6,5,1];
function uniq4(arr){
    if (arr.length <= 1) { return arr; }
    return arr.reduce((pre,cur) => {
        return pre.includes(cur) ? pre : [...pre,cur].sort((a,b) => a-b);
    },[]);
}
console.log(uniq4(arr4));　　   // [1, 2, 3, 4, 5, 6]

// map  object
let arr5 = [1,4,3,6,4,5,1,2,4,7,5];
function uniq5(arr){
    if (arr.length <= 1) { return arr; }
    let map = new Map();
    let result = [];
    for(let i = 0;i<arr.length;i++){
        if(!map.has(arr[i])){
            map.set(arr[i],true);
            result.push(arr[i])
        }
    }
    result.sort((a,b) => a - b);
    return result;
}
console.log(uniq5(arr5));   　　//[1, 2, 3, 4, 5, 6, 7]

let arr6 = [1,4,3,6,4,5,1,2,4,7,5,5,4,6];
function uniq6(arr){
    if (arr.length <= 1) { return arr; }
    let obj = {};
    let result = [];
    for(let i = 0;i<arr.length;i++){
        if(!obj[arr[i]]){
            obj[arr[i]] = true;
            result.push(arr[i]);
        }
    }
    result.sort((a,b) => a - b);
    return result;
}
console.log(uniq6(arr6));   　　//[1, 2, 3, 4, 5, 6, 7]

// splice
let arr7 = [1,4,3,6,4,5,8,1,2,8,4,7,5];
function uniq7(arr){
    if (arr.length <= 1) { return arr; }
    for(let i = 0;i<arr.length;i++){
        for(let j = i+1;j<arr.length;j++){
            if(arr[i] === arr[j]){
                arr.splice(j,1);
                j--;
            }
        }
    }
    arr.sort((a,b) => a - b);
    return arr;
}
console.log(uniq7(arr7));   　　//[1, 2, 3, 4, 5, 6, 7, 8]

若有錯誤或者不足還望指正，謝謝！！！