array.find [method]

array.find( var item[, bool strict[, int from ]] )

attempts to find item in array, starting from 0 or the index passed with from, if it exists, using basic or strict equality comparisons (depending on strict), returning the index or 'null' if item was not found

a = [ 5, 6, 7, 8 ];
a.find( "7" ); // returns 2
a.find( "7", true ); // returns null