使用reduce的Javascript重构映射示例

作为练习,我正在尝试将地图示例转换为使用reduce:

const numbers = [1, 2, 3, 4];

numbers.map(function(a,b) {
    return a+b;
});
// [1, 3, 5, 7]

我尝试使用reduce的相同示例:

numbers.reduce(
  (sum, elem) => {
    sum.push(elem + elem); // how can one add the index of array to the number instead of doubling it?
    return sum;
  }, []);
// [2, 4, 6, 8], instead I want: [1, 3, 5, 7]

Suren Srapya.. 5

你的结果减少了.传递第三个参数,即索引

const numbers = [1, 2, 3, 4];


var arr = numbers.reduce(
  (sum, elem, index) => {
    sum.push(elem + index);
    return sum;
  }, []);

console.log(arr);

1 -> 1 + 0 (index) = 1
2 -> 2 + 1 (index) = 3
3 -> 3 + 2 (index) = 5
4 -> 4 + 3 (index) = 7

const numbers = [1, 2, 7, 4];

var arr = numbers.map(function(a,b) {
    return a+b;
});

console.log(arr);

1 -> 1 + 0 (index) = 1
2 -> 2 + 1 (index) = 3
7 -> 7 + 2 (index) = 9
4 -> 4 + 3 (index) = 7

const numbers = [1, 2, 3, 4];


var arr = numbers.reduce(
  (sum, elem, index) => {
    sum.push(elem + index);
    return sum;
  }, []);

console.log(arr);