How to use if statements in underscore js templates

Question

I m using the underscore js templating function and have done a template like this     lt script type  text template  id  gridItem  gt       lt div class  griditem  lt    gridType   gt   lt    gridSize   gt   gt           lt img src   lt    image   gt     gt           lt div class  content  gt               lt span class  subheading  gt  lt    categoryName   gt  lt  span gt               lt   if  date      gt  lt span class  date  gt  lt    date   gt  lt  span gt  lt        gt               lt h2 gt  lt    title   gt  lt  h2 gt           lt  div gt       lt  div gt   lt  script gt    As you can see I have an if statement in there because all of my models won t have the date parameter  However this way of doing it gives me an error date is not defined  So  how can I do if statements within a template

User · Answer

You can try   isUndefined   lt   if     isUndefined date       gt  lt span class  date  gt  lt    date   gt  lt  span gt  lt       gt

User · Answer

To check for null values you could use   isNull from official documentation  isNull  isNull object    Returns true if the value of object is null     isNull null     gt  true   isNull undefined     gt  false

User · Answer

Depending on the situation and or your style  you might also wanna use print inside your  lt     gt  tags  as it allows for direct output  Like    lt   if  typeof id      undefined          print id     else       print  new Model        gt    And for the original snippet with some concatenation    lt   if  typeof date      undefined         print   lt span class  date  gt     date     lt  span gt         gt

User · Answer

Here is a simple if else check in underscore js  if you need to include a null check    lt div class  editor-label  gt       lt label gt First Name    lt  label gt   lt  div gt   lt div class  editor-field  gt       lt   if FirstName    null      gt           lt input type  text  id  txtFirstName  value      gt       lt     else     gt           lt input type  text  id  txtFirstName  value   lt   FirstName  gt     gt       lt       gt   lt  div gt

User · Answer

This should do the trick    lt   if  typeof date       undefined       gt       lt span class  date  gt  lt    date   gt  lt  span gt   lt       gt    Remember that in underscore js templates if and for are just standard javascript syntax wrapped in  lt     gt  tags

User · Answer

Responding to blackdivine above  about how to stripe one s results   you may have already found your answer  if so  shame on you for not sharing    but the easiest way of doing so is by using the modulus operator  say  for example  you re working in a for loop    lt   for i 0  l myLongArray length  i lt l    i      gt       lt       gt    Within that loop  simply check the value of your index  i  in my case     lt   if i 2      gt class  odd  lt     else     gt class  even   lt      gt    Doing this will check the remainder of my index divided by two  toggling between 1 and 0 for each index row

User · Answer

If you prefer shorter if else statement  you can use this shorthand    lt    typeof id      undefined     id        gt    It means display the id if is valid and blank if it wasn t

User · Answer

From here    You can also refer to the properties of the data object via that object  instead of accessing them as variables   Meaning that for OP s case this will work  with a significantly smaller change than other possible solutions     lt   if  obj date      gt  lt span class  date  gt  lt    date   gt  lt  span gt  lt        gt

[javascript] How to use if statements in underscore.js templates?

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