(I) The string type
⑴ string needs to be quoted in JS
⑵ use double or single quotes can be, but do not use Hunzhuo
⑶ can not be nested quotes, double quotes not put double quotes, single quotes not put single quotes
⑷ in the string, can be used "\" as an escape character, when expressed special symbols can be used "\" escape
⑸ output literal string str
alert("str");
Output variable str
alert(str);
㈡Number type
1. JS Number values are all types, including integer and floating point (decimal)
// number 123
var A = 123;
// string 123
var B = "123";
2. typeof operator can use to check a type of a variable
Syntax: typeof variable
Check the string, it returns string
Check value, it will return number
3.JS may represent the maximum number:
Number.MAX_VALUE 1.7976931348623157e+308
4.JS numbers can represent a minimum value:
Number.MIN_VALUE 5e-324 is greater than the minimum value of 0
Number 5. If digital representation exceeds the maximum, it returns a Infinity
Infinity represents positive infinity - Infinity representing negative infinity
Infinity is a literal, it is designed to represent a positive infinity
Infinity will return with a check number typeof
6.NaN is a special number, indicates Not A Number
NaN is a literal, so do not add "" double quotes
Use typeof NaN also returns a check number
7. integer in JS ensure accurate operation can be substantially
If a floating-point operations for JS, inaccurate results may not be a
So do not use JS to carry out precision operations require a relatively high