如何添加到数组中的数组 JavaScript

Question

I have an array:

["1", "2","3","4","5"]

that I would like to change to:

[["1, 0 ,0 ,0"], ["2, 0, 0, 0"],["3,0,0,0"],["4,0,0,0"],["5,0,0,0"]]

I've tried to achieve this with the following code:

var arr1 = ["1", "2","3","4","5"];
var arr2 = [,"0", "0","0"];

for(var z=0; z<arr1.length; z++)
    {
    arr1[z] = arr1[z].concat(arr2);
    console.log(arr1)
    }
 

However, this doesn't achieve what I want and places commas between each item, which I think is because it is not a string? I've tried using.join too but I couldn't get that to work either. Could someone point me in the right direction for this please? Thanks.

Answer 1

Please try the following example

 const array = ["1", "2", "3", "4", "5"]; const output = array.map((entry) => [`${entry}, 0, 0, 0`]); console.log(output);

See

• Array.prototype.map()
• Template literals (Template strings)

Answer 2

if it's set in stone, you can do

let arr = []

var arr1 = ["1", "2","3","4","5"];
var arr2 = ["0", "0","0"];

arr1.forEach(el=>arr.push([el, ...arr2]));


console.log(arr)

Answer 3

You first need to convert each element to array and then append the second array to the newly converted array element. The following code snippet would make it clear -

 var arr1 = ["1", "2", "3", "4", "5"]; var arr2 = [ "0", "0", "0"]; for (var z = 0; z < arr1.length; z++) { // First convert the element into a list arr1[z] = [arr1[z]]; // Then append the second array to it arr1[z] = arr1[z].concat(arr2); // Another way - //arr1[z].push(...arr2); } // Final array - console.log(arr1);

---

Using Map():

Another way to do it would be using map() as below -

 var arr1 = ["1", "2", "3", "4", "5"]; var arr2 = [ "0", "0", "0"]; arr1 = arr1.map(el=>[el,...arr2]); console.log(arr1);

---

Using ForEach()

You could also do it using forEach() method -

 var arr1 = ["1", "2", "3", "4", "5"]; var arr2 = [ "0", "0", "0"]; // this will note mutate original arr1 and store result in res let res = []; //... is the spread operator which will allows iterable objects to be expanded in place arr1.forEach(el=>res.push([el,...arr2])); // final result console.log(res);

---

There's probably numerous other ways as well... These were just few I have listed. You could even do it using naive nested loops method if you don't know anything about map() , forEach() , or concat() / push() methods.

Hope this helps !

Answer 4

Use map to go through each of your element and append the array with zeros, transform it to a string and wrap in an array again which will hold one value

 const a = ["1", "2", "3", "4", "5"] const arr = [0, 0, 0, 0]; const res = a.map(x => [ [x, ...arr].join() ]) console.log(res)