Logical OR Operator

Overview

Logical OR operator is a shortcut operator, and when using || and LHS is false, the RHS will be evaluated.

var b = a || 10;    // initializing 10 when a is false.

This can be also used with assignment operator as ||=.

a ||= new A();  // creating an instance only when a is false.

Examples

Example 1. Simple use

Code

function test(a) {
    return a || 10;
}

System.println(test(0));
System.println(test(1));
System.println(test(null));

Result

10
1
10

Example 2. With assignment

Code

var id;
class A() { @id = id++; }

function test(a) {
    a ||= new A();
    return a;
}

var a;
id = 10;
System.println((a = test(a)).id);
System.println((a = test(a)).id);
System.println((a = test(a)).id);

Result

10
10
10