Website is upgrading. We will get back soon with latest updates. Thanks for your kind support.


Suggested keywords:

{} + [] is not 0


The thing to keep in mind about coercing objects like arrays to primitives, is they usually become strings first. So coercing an empty object to a number goes like this:

+ {};
// "[object Object]"
// NaN

But the toString for an array happens to be capable of producing a number of valid number strings. It converts each element to a string, and then joins them with commas. That means for single element arrays, it effectively just drops the array. And for empty arrays those become empty strings which become 0. For reasons.

+ [1, 2, 3];
// "1,2,3"
// NaN

+ [4];
// "4"
// 4

+ []:
// ""
// 0

As for undefined and null. Yeah. That’s just what the spec says to do, so that’s how it works.

You should write because you love the shape of Flow and sentences and the creation of different words on a page.
Social Media

Leave a Reply


to Our Newsletter