Why it works in nodejs or any other javascript compiler?

Question

I was testing the filter function for an array of objects, but by mistake I defined b as an array of numbers, so I decided to see if the filter function gives me an error if I accessed an invalid property, but unexpectedly it works, and i don't know why, could someone explain to me why it works?

a = {a:5};
b = [1,2,3,4,5];
console.log(b.filter(x => x.z === a.a.z).pop()); // 5

`5.z` is a SyntaxError, but `let x = 5; let y = x.z;` is valid, and `y` has the value undefined. — jarmod, Sep 22 '20 at 23:29

score 2 · Accepted Answer · answered Sep 22 '20 at 23:25

2

a.a is 5. a.a.z is undefined.

x is always a number. x.z is undefined.

undefined === undefined

The filter copies all the values in the array.

Pop pulls the last value off the array. It is 5.

answered Sep 22 '20 at 23:25

Quentin

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Why it works in nodejs or any other javascript compiler?

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