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Number is the built-in object corresponding to the primitive number data type. As discussed in Chapter 3, all numbers are represented in IEEE 754-1985 double-precision floating-point format. This representation is 64 bits long, permitting floating-point magnitudes as large as ±1.7976ґ10308 and as small as ±2.2250ґ10-308. The Number() constructor takes an optional argument specifying its initial value:

var x = new Number();
var y = new Number(17.5);

Table 7-5 lists the special numeric values that are provided as properties of the Number object.

Table 7-5: Properties of the Number Object




Largest magnitude representable


Smallest magnitude representable


The special value Infinity


The special value -Infinity


The special value NaN

The only useful method of this object is toString(), which returns the value of the number in a string. Of course it is rarely needed, given that generally a number type converts to a string when we need to use it as such.

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