数组去重

1.filter 去重

    const list = [1, 2, 3, 4, 1, 2, 3, 4, 5];
    // filter 去重
    const newList = list.filter((item, index, array) => {
      return array.indexOf(item) === index;
    });
    console.log(newList);

2.new Set 去重

    const list = [1, 2, 3, 4, 1, 2, 3, 4, 5];
    // new Set 去重
    const oneList = [...new Set(list)];
    console.log(oneList);

3.reduce+includes 去重

    const twoList = list.reduce((array, b) => {
        return array.includes(b) ? [...array] : [...array, b];
     }, []);
    console.log(twoList);

4.reduce+indexOf 去重

    const twoList = list.reduce((array, b) => {
      const bol = !!~array.indexOf(b);
      return bol ? [...array] : [...array, b];
    }, []);
    console.log(twoList);

5.reduce 去重数组对象

   const list = [
      { a: 1, b: 2 },
      { a: 1, b: 2 },
      { a: 1, b: 3 },
    ];
    const twoList = list.reduce((array, b) => {
      const bol = !!~JSON.stringify(array).indexOf(JSON.stringify(b));
      return bol ? [...array] : [...array, b];
    }, []);
    console.log(twoList); // [ { a: 1, b: 2 },   { a: 1, b: 3 }]