Core JavaScript 1.5 Reference:Global Objects:Number:POSITIVE INFINITY
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[edit] Summary
A value representing the positive Infinity value.
| Property of Number | |
| Implemented in: | JavaScript 1.1, NES 2.0 |
| ECMA Version: | ECMA-262 |
[edit] Description
The value of Number.POSITIVE_INFINITY is the same as the value of the global object's Infinity property.
This value behaves slightly differently than mathematical infinity:
- Any positive value, including POSITIVE_INFINITY, multiplied by POSITIVE_INFINITY is POSITIVE_INFINITY.
- Any negative value, including NEGATIVE_INFINITY, multiplied by POSITIVE_INFINITY is NEGATIVE_INFINITY.
- Zero multiplied by POSITIVE_INFINITY is NaN.
- NaN multiplied by POSITIVE_INFINITY is NaN.
- POSITIVE_INFINITY, divided by any negative value except NEGATIVE_INFINITY, is NEGATIVE_INFINITY.
- POSITIVE_INFINITY, divided by any positive value except POSITIVE_INFINITY, is POSITIVE_INFINITY.
- POSITIVE_INFINITY, divided by either NEGATIVE_INFINITY or POSITIVE_INFINITY, is NaN.
- Any number divided by POSITIVE_INFINITY is Zero.
Several JavaScript methods (such as the Number constructor, parseFloat, and parseInt) return NaN if the value specified in the parameter is significantly higher than Number.MAX_VALUE.
You might use the Number.POSITIVE_INFINITY property to indicate an error condition that returns a finite number in case of success. Note, however, that isFinite would be more appropriate in such a case.
[edit] Example
In the following example, the variable bigNumber is assigned a value that is larger than the maximum value. When the if statement executes, bigNumber has the value "Infinity", so bigNumber is set to a more manageable value before continuing.
var bigNumber = Number.MAX_VALUE * 2
if (bigNumber == Number.POSITIVE_INFINITY) {
bigNumber = returnFinite();
}