数组去重方法总结

数组去重

let arr = [{ name: "fct" }, { name: "fct" }, 1, 3, 4, 1, 4, 6];
// 1.Set
let newArr = Array.from(new Set(arr));
// let newArr = [...new Set(arr)]
console.log(newArr);// [{…}, {…}, 1, 3, 4, 6]

// 2.循环实现
function unique(arr) {
    let len = arr.length;
    for (let i = 0; i < len; i++) {
        for (let j = i + 1; j < len; j++) {
            if (arr[i] === arr[j]) {
                arr.splice(j, 1);//删除一项
                len--;  //长度减小
                j--;    // j 下标减 1
            }
        }
    }
    return arr;
}
console.log(unique(arr));

// 3.indexOf
function unique1(arr) {
    let newArr = [];
    for (let i = 0; i < arr.length; i++) {
        if (newArr.indexOf(arr[i]) === -1) {
            newArr.push(arr[i]);
        }
    }
    return newArr;
}
console.log(unique1(arr));

// 4. includes
function unique2(arr) {
    let newArr = [];
    for (let i = 0; i < arr.length; i++) {
        if (!newArr.includes(arr[i])) {
            newArr.push(arr[i]);
        }
    }
    return newArr;
}
console.log(unique2(arr));

// 5. filter
function unique3(arr) {
    return arr.filter((item, index) => {
        return arr.indexOf(item, 0) === index
    })
}
console.log(unique3(arr));