Math.PI // π
Math.E // e: The base of the natural logarithm
Math.sqrt(3) // The square root of 3
Math.pow(3,1/3) // The cube root of 3
Math.sin(0) // Trig: also Math.cos, Math.atan, etc.
Math.log(10) // Natural logarithm of 10
Math.log(100)/Math.LN10 // Base 10 logarithm of 100
Math.log(512)/Math.LN2 // Base 2 logarithm of 512
Math.exp(3) // Math.E cubed
Arithmetic in JavaScript does not raise errors in cases of over-
flow, underflow, or division by zero. When the result of a nu-
meric operation is larger than the largest representable number
(overflow), the result is a special infinity value, which Java-
Script prints as Infinity. Similarly, when a negative value be-
comes larger than the largest representable negative number,
the result is negative infinity, printed as -Infinity. The infinite
values behave as you would expect: adding, subtracting, mul-
tiplying, or dividing them by anything results in an infinite
value (possibly with the sign reversed).
Division by zero is not an error in JavaScript: it simply returns
infinity or negative infinity. There is one exception, however:
zero divided by zero does not have a well-defined value, and
the result of this operation is the special not-a-number value,
printed as NaN. NaN also arises if you attempt to divide infinity
by infinity, or take the square root of a negative number or use
arithmetic operators with nonnumeric operands that cannot
be converted to numbers.
JavaScript predefines global variables Infinity and NaN to hold
the positive infinity and not-a-number value.
The not-a-number value has one unusual feature in JavaScript:
it does not compare equal to any other value, including itself.
This means that you can’t write x == NaN to determine whether
the value of a variable x is NaN. Instead, you should write x !=
x. That expression will be true if, and only if, x is NaN. The
function isNaN() is similar. It returns true if its argument is
NaN, or if that argument is a nonnumeric value such as a string
or an object. The related function isFinite() returns true if its
argument is a number other than NaN, Infinity, or -Infinity.
8 | Chapter 2: Types, Values, and Variables
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