JavaScript check if value is only undefined null or false

Question

Other than creating a function  is there a shorter way to check if a value is undefined null or false only in JavaScript   The below if statement is equivalent to if val   null  amp  amp  val   undefined val   false  The code works fine  I m looking for a shorter equivalent   if val  null    val   false           Above val  null evaluates to true both when val undefined or val null   I was thinking maybe using bitwise operators  or some other trickery

User · Answer

Try like Below  var Boolify   require  node-boolify   Boolify  if   Boolify val           your instruction     Refer node-boolify

User · Answer

One way to do it is like that   var acceptable     undefined   1   boolean   1   object   1    if  val  amp  amp  acceptable typeof val                 I think it minimizes the number of operations given your restrictions making the check fast

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only shortcut for something like this that I know of is   var val   val  null    val   false    false  true

User · Answer

Well  you can always  give up      function b val       return  val  null    val   false

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Another solution   Based on the document  Boolean object will return true if the value is not 0  undefined  null  etc  https   developer mozilla org en-US docs Web JavaScript Reference Global Objects Boolean     If value is omitted or is 0  -0  null  false  NaN  undefined  or the empty string       the object has an initial value of false     So  if Boolean val       executable

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I think what you re looking for is   val  false which can be turned to  val  even shorter    You see   function checkValue value        console log   value      checkValue       false checkValue null      false checkValue undefined      false checkValue false      false checkValue         false  checkValue true      true checkValue         true checkValue  any string       true   That works by flipping the value by using the   operator   If you flip null once for example like so     console log  null     that would output -- gt  true   If you flip it twice like so    console log   null     that would output -- gt  false   Same with undefined or false   Your code   if val  null    val   false           would then become   if  val            That would work for all cases even when there s a string but it s length is zero  Now if you want it to also work for the number 0  which would become false if it was double flipped  then your if would become   if  val  amp  amp  val     0         code runs only when val    null  undefined  false  or empty string

User · Answer

Using   is much cleaner   var   function if exists     function if doesnt exist

User · Answer

Boolean val      false   This worked for me to check if value was falsely

User · Answer

The best way to do it I think is    if val    true     do something      This will be true if val is false  NaN  or undefined

[javascript] JavaScript check if value is only undefined, null or false

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