Using Javascript numbers

How to use Javascript numbers.

  • In Javascript all numbers are represented as floating-point with values from ±5 x 10-324 to ±1.7976931348623157 x 10+308.
    var i=1; // integer
    var f=3.2345; // float
  • Usually you write number values in base-10, but you can express values as hexadecimal (base-16) values or as octal (base-8) as well.
    // A hexadecimal literal begins with "0x" or "0X"
    // followed by a sequence of hexadecimal digits:
    // 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
    var h=0xf0;  // 15*16 + 0 = 240 (base 10)
    var h=0xfff;  // 15*16*16 + 15*16 + 15 = 4095 (base 10)
    // A octal literal begins with "0"
    // followed by a sequence of octal digits:
    // 0,1,2,3,4,5,6,7
    var h=070;  // 7*8 + 0 = 56 (base 10)
  • Floating-point is represented as the integral part of the number, followed by a decimal point and the fractional part of the number.
    var x=.333333333333333333;
    var y=6789.3476;
  • You can also express the floating-point values with exponential notation. This is done by putting the character e (or E) after the decimal digits, followed by an optional plus or a minus sign, followed by an integer exponent.
    // The full floating value syntax is then:
    // [digits][.digits][(E|e)[(+|-)]digits]
    var f=32.12345E-32;  // 32.12345 * 10-32
    var z=31.567e23;     // 31.567 * 1023
  • Javascript have some global numeric constants:
    Constant Meaning
    Infinity Special value to represent infinity. When a floating-point value becomes larger than the largest representable finite number.
    NaN Special Not-a-Number value. (when a mathematical operation (such as division of zero by zero) yields an undefined result or an error.)

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