Number

Objectives

• convert strings into numbers
• convert numbers into strings
• use methods of the JavaScript Number object
• use built-in Number object variables

Converting between strings and numbers

• parseInt(string): looks for a valid integer starting at the beginning of the string and returns it as a number if found, or NaN if none is found; ignores the string past the first valid integer
• parseInt(string, radix): looks for a valid integer in base radix starting at the beginning of the string and returns it as a number if found, or NaN if none is found; ignores the string past the first valid integer
• parseFloat(string): looks for a valid floating point number starting at the beginning of the string and returns it as a number if found, or NaN if none is found; ignores the string past the first valid floating-point number
• .toString(): returns the string representation of the numeric value contained in the number object it is called on
• .toString(radix): returns the string representation of the numeric value contained in the number object it is called on; the number should be in base radix, but there is no guarantee
• .toExponential(n): returns a representation of the number object in exponential format using n digits after the decimal
• .toFixed(n): returns a representation of the number object using n digits after the decimal
• .toPrecision(n): returns a representation of the number object using n digits of significance
• .valueOf(): returns the primitive numeric value of the number object
• you can convert a string to a number by prepending a + sign
• you can convert a string to a number by multiplying by 1

Number constants

• Number.MAX_VALUE: the largest numeric value JavaScript can represent
• Number.MIN_VALUE: the smallest numeric value JavaScript can represent
• Number.POSITIVE_INFINITY: positive infinity (occurs on overflow)
• Number.NEGATIVE_INFINITY: negative infinity (occurs on overflow)
• Number.NaN: used to represent a non-numeric value

Useful functions

• isNaN(n): returns true if n is not a legal number
• isFinite(n); returns true iff n represents a finite numeric value