Logical AND Operator

Overview

Logical AND operator is a shortcut operator, and when using && and LHS is true, the RHS will be evaluated.

var b = a && 10;    // initializing 10 when a is true.

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

a &&= func();       // calling func and assign it to the variable of a, only when a is true.

Examples

Example 1. Simple use

Code

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

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

Result

0
10
null

Example 2. With assignment

Code

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

function test(a) {
    a &&= new A();
    return a ?? { id: 1 };
}

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

Result

1
10
11