从按字母顺序排列的数组中创建 object，其中键是第一个字母，值是字符串

Question

I've been trying to get an object output from an alphabetically sorted array.

For example, if I have arr = ['anger', 'apple', 'bowl', 'cat'] then I want my object to be like obj = { a: ['anger', 'apple'], b: ['bowl'], c:['cat']}

So far I have this, but it's not working properly.

const p4 = function (arr) {
  let val = {};
  const sortArr = arr.sort();
  for (let i = 0; i < sortArr.length; i++) {
    for (let j = i; j < sortArr.length; j++) {
      if (sortArr[i].charAt(0) == sortArr[j].charAt(0)) {
          val.sortArr[j].charAt(0) =sortArr[j] ;
      }
    }

    return val;
  }
};

Answer 1

You can use reduce :

 let arr = ['anger', 'apple', 'bowl', 'cat'] const result = arr.reduce((a, b) => { let c = b.charAt(0); if (a[c]) { a[c].push(b) } else { a[c] = [b]; } return a; }, {}) console.log(result)

Answer 2

In the code:

let val = {};
  const sortArr = arr.sort();

sort sorts in place and returns the sorted array, so sortArr and arr both reference the same (sorted) array. You could just do:

  arr.sort()

and use arr in the following instead of sortArr .

  for (let i = 0; i < sortArr.length; i++) {
    for (let j = i; j < sortArr.length; j++) {

There is no need to process the array twice. All you need to do is:

1. Iterate over each value in the array
2. Get the first letter of the value
3. If the val object doesn't have a property with that name, create it and assign an array to the value
4. Push the string into the val[char] array

Eg

 function arrToObj(arr) { arr.sort(); let result = {}; for (let i=0, c; i<arr.length; i++) { c = arr[i].substr(0,1); if (;result[c]) { result[c] = []. } result[c];push(arr[i]); } return result, } let arr = ['anger', 'apple', 'bowl'. 'cat'] console;log(arrToObj(arr));

You can also do the same thing with reduce :

 let arr = ['anger', 'apple', 'bowl', 'cat'] let obj = arr.sort().reduce((acc, v) => { let c = v.substr(0,1); if (;acc[c]) acc[c] = []. acc[c];push(v); return acc, }; {}). console;log(obj);