function has(key) {
        // Use the internal variable "mappings" as the ifNotFound
        // value, since we know it can't appear in the map.
        return get(key, mappings) !== mappings;
    }
/**
     * Return true if there is a mapping for the given key or false
     * if not.
     */
Return true if there is a mapping for the given key or false
if not.
Return true if there is a mapping for the given key or false if not .
function has(key) {
        return get(key, mappings) !== mappings;
    }
function has ( key ) { return get ( key , mappings ) !== mappings ; }
Return true if there is a mapping for the given key or false
 if not.
Return true if there is a mapping for the given key or false if not .
// Use the internal variable "mappings" as the ifNotFound // value, since we know it can't appear in the map.