Can I use chained comparison operator syntax?

Question

In one JS library I saw such syntax:

if (val > 5 == t) { ... }

I tested this in console:

1 == 1 == 2 // false
2 > 1 =         


        

Answer 1

Javascript does not support the chained comparison syntax used in mathematics:

1 < 2 < 3 // 1 is less than 2 which is less than 3.

Instead, it evaluates each comparison left to right, which can sometimes yield the same results as mathematical chained comparison, as do all your examples, but the process is different:

1 < 2 < 3 // "1 is less than 2" is true, true is 1, "1 is less than 3" is true.
          // Javascript returns true.

3 < 2 < 1 // "3 is less than 2" is false, false is 0, "0 is less than 1" is true.
          // Javascript returns true.

For this reason, it should be discouraged.

To answer your question, however, yes it can be used.