Node.js Tutorial - Node.js Numbers

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All numbers in JavaScript are 64-bit IEEE 754 double-precision floating-point numbers.

All numbers in JavaScript have the same floating point number type.

Arithmetic operations (+,-,*,/,%) work on numbers as you would expect.

var myData = 1; 
var myValue = 2; 
console.log(myData + 1); 
console.log(myData / myValue); 
console.log(myData * myValue); 
console.log(myData - myValue); 
console.log(myData % 2);

The code above generates the following result.

Example

The number type in JavaScript behaves much like integer data types in other languages:

console.log(1024 * 1024);

The code above generates the following result.

The tricky part of using the number type, however, is that for many numeric values, it is an approximation of the actual number.

For example:

console.log(0.1 + 0.2);

The code above generates the following result.

When performing floating-point mathematical operations, we cannot manipulate arbitrary real numbers and expect an exact value:

console.log(1 - 0.3 + 0.1 == 0.8);

The code above generates the following result.

Note

In JavaScript dividing a number by zero returns the value Infinity or -Infinity instead of generating a runtime exception:

console.log(5 / 0);
console.log(-5 / 0);

The code above generates the following result.

Infinity and -Infinity are valid values that we can compare against in JavaScript:

var x = 10, y = 0;
console.log(x / y == Infinity);

The code above generates the following result.

Note 2

You can use the functions parseInt and parseFloat to convert strings to numbers:

console.log(parseInt("32"));
console.log(parseFloat("8.24"));
console.log(parseInt("234.12345"));
console.log(parseFloat("10"));

The code above generates the following result.

Note 3

If we provide these functions with not-parsable value, they return the special value NaN:

console.log(parseInt("cat"));
console.log(parseFloat("css"));

The code above generates the following result.

To test for NaN, use the isNaN function:

isNaN(parseInt("cat"));

Note 4

To test whether a given number is a valid finite number, use the isFinite function:

console.log(isFinite(10/5));
console.log(isFinite(10/0));
console.log(isFinite(parseFloat("css")));

The code above generates the following result.

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