Returns the index of an item in {object} where {expr} is v:true. {object} must be a |List| or a |Blob|. If {object} is a |List|, evaluate {expr} for each item in the List until the expression is v:true and return the index of this item. If {object} is a |Blob| evaluate {expr} for each byte in the Blob until the expression is v:true and return the index of this byte. {expr} must be a |string| or |Funcref|. If {expr} is a |string|: If {object} is a |List|, inside {expr} |v:key| has the index of the current List item and |v:val| has the value of the item. If {object} is a |Blob|, inside {expr} |v:key| has the index of the current byte and |v:val| has the byte value. If {expr} is a |Funcref| it must take two arguments: 1. the key or the index of the current item. 2. the value of the current item. The function must return |TRUE| if the item is found and the search should stop. The optional argument {opts} is a Dict and supports the following items: startidx start evaluating {expr} at the item with this index; may be negative for an item relative to the end Returns -1 when {expr} evaluates to v:false for all the items. Example: :let l = [#{n: 10}, #{n: 20}, #{n: 30}] :echo indexof(l, "v:val.n == 20") :echo indexof(l, {i, v -> v.n == 30}) :echo indexof(l, "v:val.n == 20", #{startidx: 1}) Can also be used as a |method|: mylist->indexof(expr)