When either the equality operator in a test for `null` or `undefined`, or the logical operator that follows it is reversed, the code has the appearance of safely null-testing the object before dereferencing it. Unfortunately the effect is just the opposite - the object is null-tested and then dereferenced only if it is `null`/`undefined`, leading to a guaranteed `TypeError`.

## Noncompliant Code Sample

    if (str == null && str.length == 0) {
      console.log("String is empty");
    }

    if (str == undefined && str.length == 0) {
      console.log("String is empty");
    }

    if (str != null || str.length > 0) {
      console.log("String is not empty");
    }

    if (str != undefined || str.length > 0) {
      console.log("String is not empty");
    }

## Compliant Solution

    if (str != null && str.length == 0) {
      console.log("String is empty");
    }

    if (str != undefined && str.length == 0) {
      console.log("String is empty");
    }

    if (str == null || str.length > 0) {
      console.log("String is not empty");
    }

    if (str == undefined || str.length > 0) {
      console.log("String is not empty");
    }