Reverse the logic of two “or” statements in JavaScript if query

问题

I have an if test in JavaScript which achieves what I want but not as elegantly as possible. It goes like this:

if (x > y || p < q) {
    // don't do anything
} else {
   doSomeFunction();
}

If there any way to flip the logic of this so there's only a single if statement without having to have a dummy if-condition as well as the else condition?

回答1:

You can use the ! operator to invert the condition:

if (!(x > y || p < q)) {
   doSomeFunction();
}

Or simply rewrite the condition like this:

if (x <= y && p >= q) {
   doSomeFunction();
}

Note: See De Morgan's laws for an explanation about why these two conditions are equivalent.

回答2:

You can simply invert the comparisons and the logical OR.

if (x <= y && p >= q) {
    doSomeFunction();
}

回答3:

Along with the other answer, the last option (less readable) is :

(x > y || p < q) || doSomeFunction();

If the left bracket is true, it will NOT execute the function.

来源：https://stackoverflow.com/questions/22967064/reverse-the-logic-of-two-or-statements-in-javascript-if-query