MDN / Subtraction assignment (-=)
MDN / Subtraction assignment (-=)
The subtraction assignment (-=) operator performs subtraction on the two operands and assigns the result to the left operand.
let a = 2;
console.log((a -= 3));
// Expected output: -1
console.log((a -= "Hello"));
// Expected output: NaN
Syntax
x -= y
Description
x -= y is equivalent to x = x - y, except that the expression x is only evaluated once.
Examples
Subtraction assignment using numbers
let bar = 5;
bar -= 2; // 3
Other non-BigInt values are coerced to numbers:
bar -= "foo"; // NaN
Subtraction assignment using BigInts
let foo = 3n;
foo -= 2n; // 1n
foo -= 1; // TypeError: Cannot mix BigInt and other types, use explicit conversions