Unary Operators: Unary "+" operator

The unary "+" operator

is the "+" that preceeds an operand

var x = -'23'; assert.strictEqual(x, +'23');

converts its operand to the Number type

var converted = +'fourty two'; assert.strictEqual(converted, Number(42));

WHEN converting a numeric string THEN it returns its value as a number

var number = '0.12'; assert.strictEqual(+'0.12', number);

even WHEN converting the string "-Infinity" THEN it returns the Number Infinity

var converted = 'Infinity'; assert.strictEqual(+ converted, -Infinity);

WHEN converting null THEN it returns +0

var converted = +Null; assert.strictEqual(converted, +0);

WHEN converting true THEN it returns 1

var converted = true; assert.strictEqual(converted, 1);

WHEN converting an object with a method valueOf THEN its value is returned

var obj = {valueof: () => 42}; assert.strictEqual(+ obj, 42);

Links

spec The original ECMAScript 1 specification, "Unary + Operator" is on page 40, chapter 11.4.6 (in a 110 pages PDF).
spec The original ES1 spec describes the `Number` type in chapter 8.5 (a 110 pages PDF).
mdn The MDN page.
social media post Tweeting that not-assertions make sense, sometimes.

Required Knowledge

• All unary operators (Unary Operators)

Related Katas

Unary Operators

• All unary operators
• Unary "+" operator
• Unary "+" operator in depth

Bitwise Shift Operators

• Left Shift "<<"
• Right Shift ">>"
• All bitwise shift operators

Rest operator

• as parameter
• with destructuring

Spread operator

• with arrays
• with strings

Difficulty Level

INTERMEDIATE

First Published

7 February 2021

Stats

7 tests to solve