Why is deep equals on two arrays with deeply equal elements yielding false?

Question

I have to arrays in javascript. Equality comparison on the elements with both === and == succeeds. But when I do a deep equals on the arrays with chai, I keep getting failure.

What am I doing wrong? Why is one array showing the element as a string. Clearly it's not actually a string, right? Otherwise the === operator would fail.

The type of the elements in the arrays is mongoose ObjectId.

The arrays:

A: ["57af9c0623a2c3b106efa7a8"]
B: [ 57af9c0623a2c3b106efa7a8 ]

A[0] === B[0] // true

The line which fails:

expect(A).to.eql(B);

`57af9c0623a2c3b106efa7a8` without double quotes doesn't look like a string or a number. It's a syntax error. This can't be what your array really looks like. — GOTO 0, Aug 13 '16 at 22:26
@discipline The type of the elements is mongoose ObjectId, I don't even know where the quotations are coming from in A. — jenny, Aug 13 '16 at 22:26
Comparison with both === and == succeeds for what? These arrays are definately not equal. One of them isn't a legal array in javascript. — Tibrogargan, Aug 13 '16 at 22:26
Try entering `[ 57af9c0623a2c3b106efa7a8 ]` in your browser's console, you'll get a syntax error: *SyntaxError: identifier starts immediately after numeric literal* — user247702, Aug 13 '16 at 22:29
Its doing that because of coercion, but your code is wrong and so is the coercion process. Your testing suite is right to say it is false but it is also a bug in your code that needs addressed. — , Aug 13 '16 at 22:29
Can you post the actual code? It appears there should be more to this that would explain how array B can even function — dunck, Aug 13 '16 at 22:30
My guess is that whatever the object `B` is has a custom `toString` method that outputs `[ 57af9c0623a2c3b106efa7a8 ]`, but it's not an array. — Jacob, Aug 13 '16 at 22:30
Alright, got it. Can't just put a mongoose objectId into an array and expect it to be valid. — jenny, Aug 13 '16 at 22:32
You can't even put equal strings in two arrays and have either `==` or `===` evaluate to true. — Tibrogargan, Aug 13 '16 at 22:35
@Tibrogargan I wasn't doing that to the arrays, read the question again. — jenny, Aug 13 '16 at 22:37

score 0 · Answer 1 · edited May 23 '17 at 12:22

0

This is two equals array but different objects.

var a = ['57af'];
var b = ['57af'];
console.log(a[0] === b[0], a === b);
---
true, false

Use to compare (from here)

isEqual = a.length == b.length && a.every(function(v,i) { return v === b[i]})

edited May 23 '17 at 12:22

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answered Aug 13 '16 at 23:13

Aikon Mogwai

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Why is deep equals on two arrays with deeply equal elements yielding false?

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