Fill every empty element with elements from another array

Question

Fill every empty element with elements from another array

I'm struggling to grasp the concept of arrays. I have two arrays and I want to replace the null elements in one with the elements from the other. Here is what I have currently:

var arr1 = [1,2,3,4]
var arr2 = [null, 99, null, null]

arr2.map((item) => {
  if (item == null) {
    arr2 = arr1.splice(item, 1)
  }
})

console.log(arr2)
// The output is [3]. I was expecting 1, 99, 3, 4

I chose to use splice as I felt it was the most appropriate method for this task. I also used .map, but it isn't a required method.

I would appreciate any guidance to a related question that has already been answered, but I couldn't find one due to English not being my primary language.

javascript arrays

Answer 1

Answer №1

Your code will execute splice(null, 1) on arr1 and then replace the entire arr2 three times.

map is a function that allows you to iterate through an array and provide a replacement for each element. Make sure to use it correctly, as shown below:

let arr1 = [1,2,3,4]
let arr2 = [null, 99, null, null]

arr2 = arr2.map((item, i) => item === null ? arr1[i] : item )

console.log(arr2)

Answer 2

Your code will execute splice(null, 1) on arr1 and then replace the entire arr2 three times.

map is a function that allows you to iterate through an array and provide a replacement for each element. Make sure to use it correctly, as shown below:

let arr1 = [1,2,3,4]
let arr2 = [null, 99, null, null]

arr2 = arr2.map((item, i) => item === null ? arr1[i] : item )

console.log(arr2)

Answer 3

Answer №2

Instead of using the splice method, you can achieve the same result by using a ternary operator to extract the value you need:

let array1 = [5, 7, 9, 2];
let array2 = [null, 18, null, null];

array2 = array2.map((value, index) => value === null ? array1[index] : value);

console.log(array2);

Answer 4

Instead of using the splice method, you can achieve the same result by using a ternary operator to extract the value you need:

let array1 = [5, 7, 9, 2];
let array2 = [null, 18, null, null];

array2 = array2.map((value, index) => value === null ? array1[index] : value);

console.log(array2);

Answer 5

Answer №3

You're heading in the right direction, however, the callback function in the map method should return the element that will be included in the new array. Here's a revised version:

arr2 = arr2.map((value, index) =>
    value != null ? value : arr1[index]
});

Answer 6

You're heading in the right direction, however, the callback function in the map method should return the element that will be included in the new array. Here's a revised version:

arr2 = arr2.map((value, index) =>
    value != null ? value : arr1[index]
});

Answer 7

Answer №4

When both arr1 and arr2 are of equal size, you can use the following method:

for(var i=0;i<arr2.length;i++){
  arr2[i]= arr2[i] || arr1[i];
}

The reason for using a for loop is to provide a clear understanding of how arrays operate, especially for those new to working with them. The || operator, also known as the null-coalescing operator, assigns the first truthy value as the result of the operation.

Answer 8

When both arr1 and arr2 are of equal size, you can use the following method:

for(var i=0;i<arr2.length;i++){
  arr2[i]= arr2[i] || arr1[i];
}

The reason for using a for loop is to provide a clear understanding of how arrays operate, especially for those new to working with them. The || operator, also known as the null-coalescing operator, assigns the first truthy value as the result of the operation.

Fill every empty element with elements from another array

Answer №1

Answer №2

Answer №3

Answer №4

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