Deleting array elements in JavaScript - delete vs splice

Question

What is the difference between using the delete operator on the array element as opposed to using the Array.splice method?

For example:

myArray = [\         


        

Answer 1

Others have already properly compared delete with splice.

Another interesting comparison is delete versus undefined: a deleted array item uses less memory than one that is just set to undefined;

For example, this code will not finish:

let y = 1;
let ary = [];
console.log("Fatal Error Coming Soon");
while (y < 4294967295)
{
    ary.push(y);
    ary[y] = undefined;
    y += 1;
}
console(ary.length);

It produces this error:

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory.

So, as you can see undefined actually takes up heap memory.

However, if you also delete the ary-item (instead of just setting it to undefined), the code will slowly finish:

let x = 1;
let ary = [];
console.log("This will take a while, but it will eventually finish successfully.");
while (x < 4294967295)
{
    ary.push(x);
    ary[x] = undefined;
    delete ary[x];
    x += 1;
}
console.log(`Success, array-length: ${ary.length}.`);

These are extreme examples, but they make a point about delete that I haven't seen anyone mention anywhere.