2021-03-18 Count the number of occurrences of array elements

Count the number of occurrences of array elements

        let arr = ['a', 'b', 'a', 'b', 'c', 'c', 'd', 'd', 'a', 1, 3, 4, 5, 6, 2, 2, 1, 2]
        //去重 转化成真实数组
        let brr = Array.from(new Set(arr))
        //将数组元素变成数组套对象
        let crr = brr.map(item => {
    
    
            return {
    
     name: item, num: 0 }
        })
        //循环判断有一样的num++
        crr.map(item => {
    
    
            for (let i in arr) {
    
    
                if (item.name == arr[i]) {
    
    
                    ++item.num
                }
            }
        })
        console.log(crr)
        // 0: {name: "a", num: 3}
        // 1: {name: "b", num: 2}
        // 2: {name: "c", num: 2}
        // 3: {name: "d", num: 2}
        // 4: {name: 1, num: 2}
        // 5: {name: 3, num: 1}
        // 6: {name: 4, num: 1}
        // 7: {name: 5, num: 1}
        // 8: {name: 6, num: 1}
        // 9: {name: 2, num: 3}

Another idea : create an object, add key, and value as num;

There are other ways to communicate with code friends~