How do I get a right computation for floating numbers in Javascript?

Question

I'm studying Javascript and I was solving a problem that involves a mathematical computation with floating numbers. I kind of heard that Javascript is weird in treating floating numbers but I was surprised when I saw its impact was this dynamic. How should I have done to get the right number for my answer? What do I need to know, to prevent this error from my future calculation? I appreciate for your help, and thank you for your time.

var merge = function(array1, array2, callback) { var result = []; for (var i = 0; i < array1.length; i++) { result.push(callback(array1[i], array2[i])); } return result; }; var euclid = function(coords1, coords2) { var myCoords = merge(coords1, coords2, function(a, b){ return a - b; }); return Math.sqrt(myCoords[0]^2 + myCoords[1]^2); }; var x = euclid([1.2, 3.67], [2.0, 4.4]); // x should now equal approximately 1.08 But instead I got: euclid([1.2, 3.67], [2.0, 4.4]); // -> 1.7320508075688772

As a general guideline, when you think a program isn't computing something correctly, use some console.log (or println) statements to figure out where the numbers start going wrong. You should have been able to figure out that myCoords[0]^2 was the problem, even if you didn't understand why it was the problem. — Teepeemm
– Teepeemm, Commented May 22, 2015 at 14:24

RichieHindle · Accepted Answer · 2015-05-22 09:41:34Z

2

If you're wanting to square a number, it's not x^2 - that's a bitwise xor.

You need Math.pow(x, 2).

edited May 22, 2015 at 9:41

answered May 22, 2015 at 9:40

RichieHindle

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2 Comments

Barmar Over a year ago

Good catch. I was just about to close this as a dupe of "Is floating point math broken"

KyleC Over a year ago

Thank you for your answer. I hadn't have a clue where to look to fix my error.

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