Augmented Assignment Operators in TypeScript: +=, -=, *= and More

In programming, it is common to use assignments to modify the contents of a variable.

Remember that everything to the right of the equals sign (=) is evaluated first, so we can say:

myVar = myVar + 5;

to add 5 to myVar.

Since this is such a common pattern, there are operators which do both a mathematical operation and assignment in one step.

One such operator is the += operator:

let myVar = 10;
myVar += 5;
console.log(myVar);

This code would print 15 to the console. We call myVar += 5 an augmented assignment.

There is one such operator for every other arithmetic operator we've learned:

For subtraction: -=

let myVar = 10;
myVar -= 5; // short for myVar = myVar - 5;
console.log(myVar); // Prints 5

For multiplication: *=

let myVar = 3;
myVar *= 5; // short for myVar = myVar * 5;
console.log(myVar); // Prints 15

For division: /=

let myVar = 20;
myVar /= 4; // short for myVar = myVar / 4;
console.log(myVar); // Prints 5

For remainder: %=

let myVar = 11;
myVar %= 3; // short for myVar = myVar % 3;
console.log(myVar); // Prints 2

For exponentiation: **=

let myVar = 3;
myVar **= 3; // short for myVar = myVar ** 3;
console.log(myVar); // Prints 27

Assignment
Follow the Coding Tutorial and let's do some augmented assignments.

Hint
Look at the examples above if you get stuck.