The equivalent to lambda expressions in Angular TypeScript (Javascript)

For filtering a list in C# we have :

var filteredList = List.Where(l => l.active);]

JS equivalent :

var filteredList = list.filter((l) => { return l.active == true; });

C# - Test for list values

var isListPopulated = List.Any( l => l.amount >= 0);

JS - Test for list values

var isListPopulated = list.filter((l) => { return l.amount >= 0; }).length > 0;

C# - Get first list item

var topItem = List.First( l => l.amount >= 0);

JS - Get first list item

var topItem = list.filter((l) => { return l.amount >= 0; })[0];

NB C# First() throws an exception if there is no match. As does the JS equivalent.

C# - Get first list item or null if none exist

var topItem = List.FirstOrDefault( l => l.amount >= 0);

JS - Get first list item or null if none exist (combo of the Any + First)

var filteredList = list.filter((l) => { return l.amount >= 0; });

var topItem = filteredList.length > 0 ? filteredList[0] : null;