It works that way:

First it calculate the left side (10 < 14) => it returns True, which is also 1.

Then it calculates the right side: (True < 50) which is (1 < 50) and this is also True.

On the other side, (10 > 7) => True = 1, but (True > 2) which is (1 > 2) is False.

If you'll try: console.log(10 < 14 == 1) you will see that it's also True.

This is not how you would check an interval in JS.

Your code would be interpreted from left to right according to operator precedence. The comparison operators are binary operators, they take a left-hand expression and a right-hand expression

10 < 15 < 50
// To
true < 50 
// To
1 < 50

// And 
10 > 7 > 2
// To
true > 2 
// To
1 > 2

You should do:

console.log(14 < 10 && 14 <50)
//
console.log(7 < 10 && 7 > 2)