数组去重

let arr = [1, 1, ‘true‘, ‘true‘, true, true, 15, 15, false, false, undefined, undefined, null, null, NaN, NaN, ‘NaN‘, ‘NaN‘, 0, 0, ‘a‘, ‘a‘, {}, {}];
function unique(arr) {
    // return [...new Set(arr)]
    return Array.from(new Set(arr))
}
console.log(unique(arr));
// [1, "true", true, 15, false, undefined, null, NaN, "NaN", 0, "a", {}, {}]

let arr = [1, 1, ‘true‘, ‘true‘, true, true, 15, 15, false, false, undefined, undefined, null, null, NaN, NaN, ‘NaN‘, ‘NaN‘, 0, 0, ‘a‘, ‘a‘, {}, {}];
function unique(arr) {
    let result = [arr[0]];
    for (let i = 1; i < arr.length; i++) {
        if (result.indexOf(arr[i]) === -1) {
            result.push(arr[i]);
        }

    }
    return result;

}
console.log(unique(arr));
//  [1, "true", true, 15, false, undefined, null, NaN, NaN, "NaN", 0, "a", {}, {}]

let arr = [2,3,1, 1, ‘true‘, ‘true‘, true, true, 15, 15, false, false, undefined, undefined, null, null, NaN, NaN, ‘NaN‘, ‘NaN‘, 0, 0, ‘a‘, ‘a‘, {}, {}];
function unique(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--;
            }
        }
    }
    return arr;

}
console.log(unique(arr));

let arr = [2, 3, 1, 1, ‘true‘, ‘true‘, true, true, 15, 15, false, false, undefined, undefined, null, null, NaN, NaN, ‘NaN‘, ‘NaN‘, 0, 0, ‘a‘, ‘a‘, {}, {}];
function unique(arr) {
    let obj = {};
    return arr.filter((item, index, arr) => {
        return obj.hasOwnProperty(typeof item + item) ? false : obj[typeof item + item] = true;
    })

}
console.log(unique(arr));