Logical AND assignment (&&=)
The logical AND assignment (x &&= y
) operator only assigns if x
is truthy.
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Syntax
js
x &&= y
Description
Logical AND assignment short-circuits, meaning that x &&= y
is equivalent to:
js
x && (x = y);
No assignment is performed if the left-hand side is not truthy, due to short-circuiting of the logical AND operator. For example, the following does not throw an error, despite x
being const
:
js
const x = 0;
x &&= 2;
Neither would the following trigger the setter:
js
const x = {
get value() {
return 0;
},
set value(v) {
console.log("Setter called");
},
};
x.value &&= 2;
In fact, if x
is not truthy, y
is not evaluated at all.
js
const x = 0;
x &&= console.log("y evaluated");
// Logs nothing
Examples
Using logical AND assignment
js
let x = 0;
let y = 1;
x &&= 0; // 0
x &&= 1; // 0
y &&= 1; // 1
y &&= 0; // 0
Specifications
Specification |
---|
ECMAScript Language Specification # sec-assignment-operators |
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