Javascript Array.from(...).forEach assignment?

Question

My code:

Array.from(document.querySelectorAll("[id^='MTG_INSTR$']") ).forEach( el => {
  el.textContent = "Test";
});

This would be pass by value and won't make the assignment from what I've read.

Array.from(document.querySelectorAll("[id^='MTG_INSTR$']") ).forEach( el => 
{

   arr[index].textContent = "test";
});

Should be a reference to each element and should work. But it's not. Is it because the array I create is unnamed, and thus I can't easily identify it?

My question - Why doesn't that second version work? It isn't making assignments on my chrome script, even though I know it's being executed. The page I'm on isn't displaying any changes, but every element beginning with MTG... should have its text content changed to "test".

It isn't. Why?

Edit:
Something like this:

Array.from(document.querySelectorAll("[id^='MTG_INSTR$']") )[0].textContent

Evaluated to the text, so I know the syntax is solid at least.

@Mr.Alien Posted the question explicitly. I'm just wondering why, in my script, that second code block isn't changing anything on the page. That edit I posted, that changes the text when I assign it something like ...[0].textContent = "tessst". (At least in console on the page) — Kevin
– Kevin, Commented Jul 2, 2017 at 8:12
By all standards, the first one should work fine... are you getting any errors? — Patrick Roberts
– Patrick Roberts, Commented Jul 2, 2017 at 8:12
@PatrickRoberts I'm a complete retard, it works fine. I intially forgot the .textContent part, but during my debugging ran into a huge post on SO talking about how it's a pass by value not reference so shouldn't commit the changes to the page, just to my new array. Jesus. — Kevin
– Kevin, Commented Jul 2, 2017 at 8:16
How your second code is even working? arr and index both should be undefined — Mr. Alien
– Mr. Alien, Commented Jul 2, 2017 at 8:17

Shanil Fernando · Accepted Answer · 2017-07-02 08:15:11Z

1

This should work fine

Array.from(document.querySelectorAll("[id^='MTG_INSTR$']") ).forEach( el => {
  el.textContent = "Test";
});

Second one should be

Array.from(document.querySelectorAll("[id^='MTG_INSTR$']") ).forEach( (el,index,arr) => 
{

   arr[index].textContent = "test";
});

answered Jul 2, 2017 at 8:15

Shanil Fernando

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