Underscore.js: how to chain custom functions

Question

Using Underscore.js, I can write the following which returns 42:

_([42, 43]).chain()
    .first()
    .value()

I have custom f

Answer 1

Not finding a tap that returns the value returns by the function is runs, I define one which I can take and add to _:

_.mixin({take: function(obj, interceptor) {
    return interceptor(obj);
}});

Then assuming I have:

function double(value) { return value * 2; };

I can write:

_([42, 43]).chain()
    .first()             // 42
    .take(double)        // Applies double to 42
    .value()             // 84

You can look at take as map on objects, instead of lists. Want to experiment with this? See this example on jsFiddle.