使用array.splice（）添加和删除特定的数组元素

Question

Is it possible to add to a specific part of an array, and then deleting a specific part of the array, in this case the end value using arr.splice() ?

i currently do this like so:

var arr = [1,2,3,4,5,6,7,8,9];
arr.splice(0,0,"test");

which should return:

"test",1,2,3,4,5,6,7,8,9

i then do:

arr.pop();

which should return:

"test",1,2,3,4,5,6,7,8

I was wondering if it's possible to do this via the arr.splice() method or if there is any cleaner method to do the same, as potentially i'll be doing this a few times, so i would end up with something like:

arr.splice(0,0,"test");
arr.pop();
arr.splice(1,0,"test2");
arr.pop();

looking at the array.splice documentation it suggests i can only delete the element in the position i'm putting the new element into, not a different one.

Answer 1

In answer to my original question as confirmed in the comments. It is not possible to provide a separate index to insert and another to remove in an array using the splice method or potentially any other single statement in javascript. The best approach to try to achieve this in a single statement if i really needed it would be to create your own function, which really seems counter productive for the most part.

Answer 2

You can use Array.from() to set the .length and values of specific indexes of an array in a single call

 var arr = [1,2,3,4,5,6,7,8,9]; arr = Array.from({length:arr.length - 1, ...arr, 0:"test"}); console.log(arr); 

To achieve the pattern described at Question you can alternatively use a loop and Object.assign()

 var arr = [1,2,3,4,5,6,7,8,9]; var n = 0; var prop = "test"; while (arr.length > 1) { Object.assign(arr, {length:arr.length -1,...arr, [n]:!n ? prop : prop+n}); ++n; console.log(arr); }