Is there a way to automatically check data equality for data type in Typescript?

Question

In Python you can do something like this

>>> a = ('a', 'b')
>>> b = ('a', 'b')
>>> a == b
True

However in Typescript

    type test = [string, string];

    var data1: test = ['a', 'b'];
    var data2: test = ['a', 'b'];

    console.log(data1 == data2);    // return false
    console.log(data1 === data2);   // return false

equality check for two data of the same type is using reference, I know I can loop through the array but are there syntactic sugar to check for data equality analogous to Python tuple ?

Nope, sorry. You'll have to resort to comparing each element of the array. I guess that's what TypeScript does for you in the background. http://stackoverflow.com/questions/3115982/how-to-check-if-two-arrays-are-equal-with-javascript — Nicklas Nygren, Apr 18 '16 at 06:17
Possible duplicate of [Object comparison in JavaScript](http://stackoverflow.com/questions/1068834/object-comparison-in-javascript) — Amid, Apr 18 '16 at 06:19
Not a duplicate as this is for Typescript which does automate a lot of stuff - but until / unless they add something like that, pointing at the Javascript answer will answer this — Rycochet, Apr 18 '16 at 08:00
you can always add an `equals` method to the `Array` prototype which does this. — Nitzan Tomer, Apr 18 '16 at 11:43

score 1 · Answer 1 · answered Apr 19 '16 at 00:49

1

Is there a way to automatically check data equality for data type in Typescript?

No. The situation is the same as in JavaScript i.e. you need a library or custom code.

answered Apr 19 '16 at 00:49

basarat

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score 1 · Answer 2 · answered May 03 '16 at 12:54

In practice, the right answer to this is almost always to use Lodash's _.isEqual function:

import _ = require("lodash");

type test = [string, string];

var data1: test = ['a', 'b'];
var data2: test = ['a', 'b'];

console.log(_.isEqual(data1, data2));

This will do deep equality comparisons for you, similarly to what you'd expect coming from other languages.

score 0 · Answer 3 · answered May 03 '16 at 13:00

TypeScript does not ship this feature off-the-shelf, the situation is completely akin to that encountered in JavaScript: you'll need to recursively scan objects (I believe Python is doing something similar under the hood).

To achieve a quick makeshift comparison for testing purposes, you could convert your values to JSON strings, then compare those strings:

JSON.stringify(data1) == JSON.stringify(data2); // true

Is there a way to automatically check data equality for data type in Typescript?

3 Answers3