CODEWITHSUNDEEP
javascriptfloating-point
Robert
Robert

Reputation: 10400

JavaScript floating point

I was wondering what the floating point limitations of JavaScript were. I have the following code that doesn't return a detailed floating point result as in:

2e-2 is the same as 0.02



var numero = 1E-12;
document.write(numero);

returns 1e-12.

What is the max exponential result that JavaScript can handle?

Upvotes: 0

Views: 317

Answers (2)

Eric Postpischil
Eric Postpischil

Reputation: 224596

JavaScript is an implementation of ECMAScript, specified in Ecma-262 and ISO/IEC 16262. Ecma-262 specifies that IEEE 754 64-bit binary floating point is used.

In this format, the smallest positive number is 2–1074 (slightly over 4.94e–324), and the largest finite number is 21024–2971 (slightly under 1.798e308). Infinity can be represented, so, in this sense, there is no upper limit to the value of a number in JavaScript.

Numbers in this format have at most 53 bits in their significands (fraction parts). (Numbers under 2–1022 are subnormal and have fewer bits.) The limited number of bits means that many numbers are not exactly representable, including the .02 in your example. Consequently, the results of arithmetic operations are rounded to the nearest representable values, and errors in chains of calculations may cancel or may accumulate, even catastrophically.

The format also includes some special entities called NaNs (for Not a Number). NaNs may be used to indicate that a number has not been initialized, for special debugging purposes, or to represent the result of an operation for which no number is suitable (such as the square root of –1).

Upvotes: 3

Andy G
Andy G

Reputation: 19367

The maximum that is less than zero..?

There is a detailed discussion here. Basically, a 0.00000x will be displayed in exponential (5 zeroes after the decimal).

Of course, you could test this for yourself ;) particularly to see if this behaviour is reliable cross-browser.

Personally, I don't think you should be concerned, or rely, on this behaviour. When you come to display a number just format it appropriately.

Upvotes: 0

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