Ternary operators in JavaScript without an else

Question

I ve always had to put null in the else conditions that don t have anything  Is there a way around it  For example  condition   x   true   null   Basically  is there a way to do the following  condition   x   true   Now it shows up as a syntax error  FYI  here is some real example code   defaults slideshowWidth   defaults slideshowWidth   obj find  img   width    px    null

User · Answer

No  it needs three operands  That s why they re called ternary operators   However  for what you have as your example  you can do this   if condition  x   true    Although it s safer to have braces if you need to add more than one statement in the future   if condition    x   true      Edit  Now that you mention the actual code in which your question applies to   if  defaults slideshowWidth        defaults slideshowWidth   obj find  img   width    px

User · Answer

To use a ternary operator without else inside of an array or object declaration  you can use the ES6 spread operator         const cond   false  const arr           cond     a             b               b    And for objects  const cond   false  const obj           cond    a  1           b  2             b  2   Original source

User · Answer

You could write  x   condition   true   x    So that x is unmodified when the condition is false   This then is equivalent to  if  condition  x   true   EDIT     defaults slideshowWidth          defaults slideshowWidth   obj find  img   width    px           null    There are a couple of alternatives - I m not saying these are better worse - merely alternatives  Passing in null as the third parameter works because the existing value is null  If you refactor and change the condition  then there is a danger that this is no longer true  Passing in the exising value as the 2nd choice in the ternary guards against this    defaults slideshowWidth            defaults slideshowWidth   obj find  img   width    px           defaults slideshowwidth    Safer  but perhaps not as nice to look at  and more typing  In practice  I d probably write  defaults slideshowWidth   defaults slideshowWidth                    obj find  img   width    px

User · Answer

var x   condition    null

User · Answer

First of all  a ternary expression is not a replacement for an if else construct - it s an equivalent to an if else construct that returns a value  That is  an if else clause is code  a ternary expression is an expression  meaning that it returns a value  This means several things   use ternary expressions only when you have a variable on the left side of the   that is to be assigned the return value only use ternary expressions when the returned value is to be one of two values  or use nested expressions if that is fitting  each part of the expression  after   and after     should return a value without side effects  the expression x   true returns true as all expressions return the last value  but it also changes x without x having any effect on the returned value   In short - the  correct  use of a ternary expression is var resultofexpression   conditionasboolean   truepart  falsepart   Instead of your example condition   x true   null    where you use a ternary expression to set the value of x  you can use this   condition  amp  amp   x   true    This is still an expression and might therefore not pass validation  so an even better approach would be  void condition  amp  amp  x   true    The last one will pass validation  But then again  if the expected value is a boolean  just use the result of the condition expression itself var x    condition      var x    foo     quot bar quot      UPDATE In relation to your sample  this is probably more appropriate  defaults slideshowWidth   defaults slideshowWidth    obj find  img   width    px

User · Answer

What about simply      if  condition    code if condition   true

User · Answer

In your case i see the ternary operator as redundant  You could assign the variable directly to the expression  using      amp  amp   operators    defaults slideshowWidth   defaults slideshowWidth   obj find  img   width    px    null     will become     defaults slideshowWidth   defaults slideshowWidth    obj find  img   width    px     It s more clear  it s more  javascript  style

User · Answer

More often  people use logical operators to shorten the statement syntax   defaults slideshowWidth  amp  amp     defaults slideshowWidth   obj find  img   width      px     But in your particular case the syntax can be even simpler  defaults slideshowWidth   defaults slideshowWidth    obj find  img   width      px    This code will return the defaults slideshowWidth value if the defaults slideshowWidth is evaluated to true and obj find  img   width      px  value otherwise  See Short-Circuit Evaluation of logical operators for details

[javascript] Ternary operators in JavaScript without an "else"

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