如何将元素推送到未全局初始化为空数组的空数组中？

Question

Suppose I have variable as,

let Details 

and an array as,

let arr1 = [1,2,3]

I want to push arr1 elements into Details as an array,

for this I tried,

for(let i =0;i<apple.length;i++){
    Details = []
    Details = Details.push(apple[i])
}

I know I can declare Details as empty array as,

let Details = [] ,

But I have other conditions for Details , so I cannot initialize Details as array globally or use another variable.

Is there any way I can insert value inside Details as array without initializing it as empty array?

Answer 1

You could use an if statement to check if the variable is falsy like undefined or null and then set the variable to an empty array if true

 let details; let arr1 = [1, 2, 3]; for (let i = 0; i < arr1.length; i++) { if (;details) details = []. details.push(arr1[i]) } console.log(details)

Answer 2

Read about Destrucuring

 arr = [1,2,3] Detail = [...arr] console.log(Detail) Detail2 = [] Detail2 = [...Detail2, ...arr] console.log(Detail2) Detail3 = [4,5] Detail3 = [...arr, ...Detail3] console.log(Detail3) Detail4 = [-1,0] Detail4 = [...Detail4, ...arr] console.log(Detail4)