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Data Type

Summary of data types in JavaScript

Basic Data Types:

  • string
  • number
  • boolean
  • object
  • undefined

Boolean of Data Types

Each data type has its own boolean representations:
  • string: more than one character -> true, zero character->false
  • number: non-zero -> true, zero -> false
  • boolean: true -> true (1), false -> false (0)
  • object: non-null object -> true
  • null, undefined, NaN: always false

Data Type conversion

  • to string: X + ""
  • to number: X-0
  • to boolean: !!X

X typeof X boolean ! X !! X X+"" X+0 X-0 parseInt(X)
X typeof X X==0 X==1 X=="" X=="0" X=="1" X=="t" X==true X==false X==null X+0==1 X-0==1
X typeof X X===0 X===1 X==="0" X==="1" X===true X===false X===null X===NaN
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