forEach(func) – calls func for every element, does not return anything.

findIndex is like find, but returns the index instead of a value.

find/filter(func) – filter elements through the function, return first/all values that make it return true.

includes(value) – returns true if the array has value, otherwise false.

indexOf/lastIndexOf(item, pos) – look for item starting from position pos, return the index or -1 if not found.

If any of items is an array, then its elements are taken. concat(.items) – returns a new array: copies all members of the current one and adds items to it.slice(start, end) – creates a new array, copies elements from index start till end (not inclusive) into it.items) – at index pos deletes deleteCount elements and inserts items. unshift(.items) – adds items to the beginning.shift() – extracts an item from the beginning,.The latter is used more often, as it’s a bit easier to understand for most people. Return user.age >= this.minAge & user.age army.canJoin(user)), that does the same.

For each javascript syntax