Compare String to null value in JavaScript

Question

I am comparing the value null to a string. However the result of the comparison is always false.

null > "a" // false

null < "a" // false

"a" > null // false

"a" > null // false

Can anyone explain why this is happening?

I did find a section (http://www.ecma-international.org/ecma-262/5.1/#sec-11.8.5) within the ECMAScript standard that seems to explain what is going on, but I do not really understand what the standard says.

Answer 1

11.8.5 is the abstract relational expression, the production relational expression is what you need to look at, which includes the abstract one.

11.8.1 The Less-than Operator ( < ) // pretty much the same as >

The production RelationalExpression : RelationalExpression < ShiftExpression is evaluated as follows:

    1) Let lref be the result of evaluating RelationalExpression.
    2) Let lval be GetValue(lref).
    3) Let rref be the result of evaluating ShiftExpression.
    4) Let rval be GetValue(rref).
--> 5) Let r be the result of performing abstract relational comparison 
       lval < rval. (see 11.8.5)
--> 6) If r is undefined, return false. Otherwise, return r.

When you look at the abstract relation comparison, the result will be undefined because Number('a') => NaN (Rule 3) which will set off these rules: If nx is NaN, return undefined or If ny is NaN, return undefined.

So 6) Let r be the result of performing abstract relational comparison, in your cases r is then undefined. The last step says if r is undefined then return false, hence your answer.

Answer 2

Both section 3 and 4 of the reference say "return false" if nothing else is true.

There simply aren't any other options given the spec you've quoted.

Not that having it be either greater or less than would make any sense anyway.