indexOf
Look for an item in a List.
    list.indexOf(item)
  
  indexOf finds the position of a given item in the List.
Parameters
- item {*}:the item to find 
Returns
 {Number}: 
the position of the item in the List, or -1 if the item is not found.
var list = new List(['Alice', 'Bob', 'Eve']);
list.indexOf('Alice');   // 0
list.indexOf('Charlie'); // -1
It is trivial to make a contains-type function using indexOf:
function(list, item) {
    return list.indexOf(item) >= 0;
}
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