Logical operators in Javascript do not always return boolean result

Given a variable myObj in Javascript, evaluating myObj.child.name || 'Kid' will cause an error if myObj.child does not exist. In comparison, in PHP, $myObj->child->name ?? 'Kid' would just yield “Kid” with no errors.

One way would be to write the expression let result = (myObj && myObj.child && myObj.child.name) ? myObj.child.name : 'Kid';.

Another way would be to take advantage of the fact that logical operators in Javascript actually return the value of one of the operands, and simply write let result = (myObj && myObj.child && myObj.child.name) || 'Kid';.

References:

• Logical Operators – Javascript MDN
• Why don’t logical operators (&& and ||) always return a boolean result?

let a = {
  x: {
    y: 2
  }
};

let result = null;
result = (a && a.x && a.x.z); // undefined, not false
result = (a && a.x && a.x.y); // 2, not true
result = (a && a.b && a.b.c) || 5; // 5
result = (q && a && a.x) || 7; // Uncaught ReferenceError: q is not defined