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JavaScript has only one type of number. Numbers can be written with or without decimals.
let x = 3.14; // A number with decimals let y = 3; // A number without decimalsYourself » Extra large or extra small numbers can be written with scientific (exponent) notation:
let x = 123e5; // 12300000 let y = 123e-5; // 0.00123Yourself »
Formula
JavaScript Numbers are Always 64 - bit Floating PointUnlike many other programming languages,
Formula
JavaScript does not define different types of numbers, like integers, short, long, floating - point etc.JavaScript numbers are always stored as double precision floating point numbers, following the international IEEE 754 standard. This format stores numbers in 64 bits, where the number (the fraction) is stored in bits 0 to 51, the exponent in bits 52 to 62, and the sign in bit 63:
Formula
Value (aka Fraction/Mantissa)Formula
52 bits (0 - 51)
11 bits (52 - 62)1 bit (63) Most programming languages have many number types:
Formula
byte (8 - bit), short (16 - bit), int (32 - bit), long (64 - bit)Formula
float (32 - bit), double (64 - bit).
Javascript numbers are always double (64 - bit floating point).Integers (numbers without a period or exponent notation) are accurate up to 15 digits.
let x = 999999999999999; // x will be 999999999999999 let y = 9999999999999999; // y will be 10000000000000000The maximum number of decimals is 17.
Floating point arithmetic is not always 100% accurate:
let x = 0.2 + 0.1;Yourself » To solve the problem above, it helps to multiply and divide:
let x = (0.2 * 10 + 0.1 * 10) / 10;WARNING !!
Formula
JavaScript uses the + operator for both addition and concatenation.Numbers are added. Strings are concatenated. If you add two numbers, the result will be a number:
let x = 10;
let y = 20;
let z = x + y;If you add two strings, the result will be a string concatenation:
let x = "10";
let y = "20";
let z = x + y;If you add a number and a string, the result will be a string concatenation:
let x = 10;
let y = "20";
let z = x + y;If you add a string and a number, the result will be a string concatenation:
let x = "10";
let y = 20;
let z = x + y;A common mistake is to expect this result to be 30:
let x = 10;
let y = 20;
let z = "The result is: " + x + y;A common mistake is to expect this result to be 102030:
let x = 10;
let y = 20;
let z = "30";
let result = x + y + z;The JavaScript interpreter works from left to right.
Formula
First 10 + 20 is added because x and y are both numbers.
Then 30 + "30" is concatenated because z is a string.JavaScript strings can have numeric content:
let x = 100; // x is a number let y = "100"; // y is a stringJavaScript will try to convert strings to numbers in all numeric operations:
let x = "100";
let y = "10";
let z = x / y;let x = "100";
let y = "10";
let z = x * y;let x = "100";
let y = "10";
let z = x - y;