如何在每次迭代后将新列添加到 javascript 中的二维数组？

Question

I have 2 arrays. (arr1, arr2) I want to take the value at index 0 and multiply it by each value in arr2, and add each value to a new row in a 2D array. ex.

arr1 = [1,3,5,7] arr2 = [4,2,1,6]

Outcome should be:

 2Darray = [
   [4,12,20,28],
   [2,6,10,14],
   [1,3,5,7],
   [6,18,30,42] 
];

Im having trouble with the for loop in javascript and how to create a new row after each iteration. ```

Thanks

Answer 1

You could map the arrays with the product of the values.

 const array1 = [1, 3, 5, 7], array2 = [4, 2, 1, 6], result = array2.map(v => array1.map(w => v * w)); result.map(a => console.log(...a)); console.log(result);

Answer 2

Using map like others said would be best.

Using the remainder operator(%) makes the most sense in my head:

const arr1 = [1,3,5,7];
const arr2 = [4,2,1,6];

var twoDemArray = [];

for (var i = 0; i < arr1.length; i++) {

  let tempArr = [];
  
  for (var j = 1; j < arr2.length+1; j++) {
    let newNum = arr1[i]*arr2[j-1];

    tempArr.push(newNum);
    
    if (j % arr2.length == 0) {
      twoDemArray.push(tempArr);
      tempArr = [];
    };
  };

};

console.log(twoDemArray)
//do stuff with twoDemArray

Answer 3

Mapping over both arrays helps.

 arr1 = [1,3,5,7]; arr2 = [4,2,1,6]; let res = arr2.map(a2 => arr1.map(a1 => a1*a2)) console.log(res);