03_ the literal of a number

Literal literals

  See what is what.  For example, if we want to represent a number in the program, we write a number. To  represent "Hello" in your program, you need to enclose the quotation marks.  These writing rules are called literal quantities. The following is a brief  explanation of the literal number and the literal character of the string.

console.log(123);console.log(你好); //这一行因为是字符串，没有引号，会产生错误

The literal amount of a number

  Number literal: That is, the number itself. No additional symbols are required.  integers  can be represented as decimal (base 10), hexadecimal (radix 16), and octal (base 8).  There can be three types of literals in JS.    Decimal (0 to 9) integers consist of numbers without leading 0,    with leading 0, 0O, and 0o in octal (0 to 7),    with leading 0x, 0X all hexadecimal (0 to f).  they are displayed with a 10 binary display.

Octal

console.log(15); //输出正 15console.log(-15); //输出负 -15console.log(07); //输出 7console.log(010); //输出 8console.log(036); //输出 30 , 3*8+6=30console.log(040); //输出 32 ，3*4+0=32console.log(0100); //输出 64 ，0*1+0*8+1*64=64console.log(0111); //输出 73 ，1*1+1*8+1*64=73

  Can only have 0~7 these few numbers, cannot have 8, 9.  if written incorrectly, it will be 10 binary.  Although it starts with 0, the number in the back is wrong and is displayed as a 10 binary.

console.log(088); //输出88

  But if the 0o (0 wow) or 0O (0 wow) starts, the following number is wrong and will error.  correct

console.log(0o77); //输出88console.log(0O77); //输出88

  Error

console.log(0o88); // 错误console.log(0O88); // 错误

Hexadecimal

  16 binary, turn 10-in: 0x2af5=5x16^0+fx16^1+ax16^2+2x16^3=10997

console.log(0xff); //255 ， 15*16^0+15*16^1=255console.log(0x2b); //13 ， 11*16^0+2*16^1=43console.log(0x11); //17

  If there is a wrong writing, that is an error.

console.log(0x2m); //出错

  The following numbers are all positive 15

console.log(15);console.log(017);console.log(0o17); //字母小写oconsole.log(0O17); //字母大写Oconsole.log(0xf);

  The numbers below are all negative 15.

console.log(-15);console.log(-017);console.log(-0o17); //字母小写oconsole.log(-0O17); //字母大写Oconsole.log(-0xf);

Decimal

The 
 allows you to use E to represent 10 of several parties, and decimals can omit the preceding 0. In a computer, a decimal number is called a  floating point number . 

console.log (3.14); //3.14 console.log ( -3.14); //-3.14 console.log (0.14); //0.14 console.log (.); //0.14 integer is 0 o'clock can omit console.log (560000); //560000 console.log (5.6e5); //560000, support index notation. 5.6*10^5 console.log (0.0001); //0.0001 console.log (1e-4); //0.0001 console.log (. 1e-3); //0.0001 can omit 0 in front of the decimal point.

  Using decimals in 8 or 16 binary will cause an error:

console.log(03.3);console.log(0x3.3);

Special Digital Literals

  Infinity infinitely large.  The following attempts to output a very large number:

console.log(3e20); //300000000000000000000console.log(3e16); //30000000000000000console.log(3e2016); //Infinityconsole.log(-3e2016); //-Infinity 负无穷大//可以直接输出 Infinityconsole.log(Infinity);console.log(-Infinity);

  How many numbers can generate Infinity, depending on the browser.  NaN is not a number.  in particular, NaN is a numeric literal.

console.log(0/0); //NaNconsole.log(6/0); //Infinityconsole.log(NaN); //NaN

  interesting phenomenon.  all operations that infinity+infinity equals Infinity nan are Nan

console.log(Infinity+Infinity) //Infinityconsole.log(Infinity-Infinity) //NaNconsole.log(Infinity+-Infinity) //NaNconsole.log(NaN+NaN) //NaNconsole.log(NaN-NaN) //NaN

03_ the literal of a number