JavaScript Number : Object

constructor primitive

A numerical value. JavaScript stores numbers as 64 bit (8 byte) double precision floats.

Number(value : Object) : Number

Coerces value to a number. Usually this method is not necessary since JavaScript will automatically coerce a value to a number when it is used in a number context. +value is another way to coerce a value to a number. This coercion is very strict and will return NaN if the specified value cannot be converted to a Number. parseInt and paseFloat can also be used to convert a String to a Number.

Example:

var one = '1';
console.log(one + 2); // 2 is converted to '2' and concatinated with '1'
console.log(Number(one) + 2); // convert '1' to a number first
console.log(+one + 2); // another way to convert to a number

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Constructors

new Number(value : Number) : Object

Creates a box for value.

Example:

var literal = 123;
var boxed = new Number(123);
literal.foo = "bar";
boxed.foo = "bar";
console.log(literal.foo);
console.log(boxed.foo);

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Instance Methods

toExponential([fractionalDigits : Number]) : String

Returns a string representation of this in scientific notation. If fractionalDigits is specified, that many digits will follow the '.'.

Example:

var x = 123.456;
console.log(x.toExponential());
console.log(x.toExponential(2));
console.log(x.toExponential(6));

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toFixed([fractionalDigits = 0 : Number]) : String

Returns a string representation of this with fractionalDigits following the '.'.

Example:

var x = 123.456;
console.log(x.toFixed());
console.log(x.toFixed(2));
console.log(x.toFixed(6));

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toLocaleString() : String

Returns a string representation of this that conforms to the number format specification of the current locale.

Example:

var x = 123.456;
console.log(x.toString());
console.log(x.toLocaleString());

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toPrecision(precision : Number) : String

Returns a string representation of this with precision significant digits.

Example:

var x = 123.456;
console.log(x.toPrecision(1));
console.log(x.toPrecision(2));
console.log(x.toPrecision(3));
console.log(x.toPrecision(4));

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toString([base = 10 : Number]) : String

Returns a string representation of this in the specified base.

Example:

var x = 0x123ABC;
console.log(x.toString());
console.log(x.toString(16));

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Number Properties

MAX_VALUE : Number

The largest possible Number less than infinity.

Example:

console.log(Number.MAX_VALUE);

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MIN_VALUE : Number

The smallest possible Number greater than 0.

Example:

console.log(Number.MIN_VALUE);

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NEGATIVE_INFINITIY : Number

Negative infinity.

Example:

console.log(Number.NEGATIVE_INFINITY);
console.log(-Infinity);
console.log(-1/0);

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NaN : Number

Floating point Not a Number. Signifies an error in a calculation. NaN is never equal to another Number, even if it is NaN. To check if something is NaN, use isNan(). Also exists as NaN in the global namespace.

Example:

console.log(Number.NaN);
console.log(NaN);
console.log(0/0);
console.log(Math.sqrt(-1));

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POSITIVE_INFINITIY : Number

Positive infinity. Also exists as Infinity in the global namespace.

Example:

console.log(Number.POSITIVE_INFINITY);
console.log(Infinity);
console.log(1/0);

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