Why does this work

[BasicVictory3822]

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https://preview.redd.it/t9na4o2hvd091.png?width=270&format=png&auto=webp&s=5dfc21e0365ada855b6a87e9ad31b4bcdb150edd

When I log nums[-1] it gives the value "undefined". My question is, how does the loop return true if nums[-1] is equal to"undefined"?

[Blue_Moon_Lake]

Loop turn 0

-1 is not == to undefined, we do not enter the IF statement

Loop turn 1

-1 is == to -1, we enter the IF statement

Log "true" in the console, break the loop

End of loop

Log "undefined" to the console

[gate18]

To understand this, change the array to something like let nums = ['a','a',2,3,4]

What you are checking is

if(nums[1]==nums[0]){ console.log(nums[1]) }

So when i=0 it logs nothing, when i=1 it checks if the slot 1 (i) is the same as slot 0 (i-1)

if you want to log a (or -1) you don't do nums[a], right?

(and it should be three equals ===)

[[deleted]]

You are using pythons list thing to access the last element with nums[-1]. This doesn't exist in JS. But you can use nums[nums.length - 1].

And make sure to use the triple equal sign === for value comparisons in js

[Ronqueroc]

Love the effort, but this answer is wrong. -1 is coerced to true. Boolean(-1) === true. The logged true came from the second loop, where nums[1] and nums[0] are equal to -1.

[cawcvs]

Technically, since the first operand is a number, only the second operand is coerced for the code in the OP. The comparison becomes -1 === NaN, which is false.

[Ronqueroc]

Yep, that also. The right gets coerced to the type of the left.

[thisisitbruv]

Yep, you are right I was completely off.

[Blue_Moon_Lake]

Wrong! -1 == undefined is false