Data type and data type conversion

Basic data types

• Digital number
• String string
• Boolean boolean
• null
• undefined

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Reference data types

• Objects
  • Ordinary objects Object
  • Array Object Array
  • Regular objects RegExp
  • Date Object Date
  ...
• Function function
...

Special type

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symbol, represents a unique value

var a = Symbol('abc'); 
var b = Symbol('abc'); 
console.log(a==b); =>false

 

Other types of digital converted (Number)

• Number (string)

Number The ('13 '); -> 13 is 
Number The ( ' 13px '); -> NaN3 // encountered as a result of non-significant digits NaN3 
Number The ('13 .5'); -> 13.5 // can be identified decimal

 

• Number (Boolean)

Number(true); //->1 
Number(false); //->0

 

• Number(null和undefined)

  Number(null); //->0 
  Number(undefined); //->NaN

   

• Number (reference type): toString first reference value into a string retrieved, and then the string is converted to a digital Number.

• parseInt和parseFloat

  parseInt('13.5px'); //=>13 
  parseFloat('13.5px'); //=>13.5
  parseInt('px123');//NaN

To convert other types to boolean (Boolean ())

Law: convert only false 0 / NaN / empty string / null / undefined, the rest is true.