which command return if label doesnt exist in item?

[mischa_spelt · Accepted solution]

If you want to know whether the label exists and has a "truthy" value, you can use the question mark:

if(current.maynotexist?) {
 // current.maynotexist exists and is non-zero, or points at a valid object
}

If you just want to know if it exists, you can do

treenode maynotexist = current.labels["maynotexist"];
if( maynotexist ) {
  // the node exists, get its value with maynotexist.value
}

However, you don't need the latter construction very often, for example, if you want to create the label if it does not exist, you can

current.labels.assert( "maynotexist" )

and if you assign a label with

current.maynotexist = 1;

it will be automatically created.

[gabriel_illescas_cavazos]

I want to set this condition for example if any label exist do nothing but if the label doesnt exist do something how can I do it?

[Jacob_Gillespie]

@Gabriel illescas Cavazos

if(!obj.MyLabel? && obj.MyLabel? != 0) {
    // Label not set
    // Do Something
}

[gabriel_illescas_cavazos]

what does it mean "!" when you star the if?

[Matthew_Gillespie]

A "!" is a logical not.

This will return true only for strings that start with h:

text.startsWith("h")

This will return true for any string that starts with any letter other than h:

!text.startsWith("h")

[vedant_g1]

I tried the ? method but it doesn't work for me