Fcombine NPM | npm.io

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A function combination utility,

Status: beta

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Annotated source code coming soon.

f.combine(f1, f2, flags) link

f.combine combines two functions. It will return a new function that invokes the two functions passed with this and arguments.

The flags object is an optional hash to set the value pre to true. If pre is true then f1 comes before f2 and f2 is considered the main function otherwise f1 is the main function. The returned function's length property matches the length property of the main function. The returned function also only returns the return value of the main function

var g = f.combine(function (a, b) {
	console.log("bar")
	return 42;
}, function (a,b,c) {
	console.log("foo")
});

g(); // "bar", "foo", returns 42
g.length === 2; // true

var h = f.combine(function () {
	return "no value";
}, function (a,b,c,d) {
	return "magic";
}, { pre: true });

h(); // "magic"
h.length === 4; // true

f.compose(f1, f2, flags)

f.compose composes two functions. It will return a new function that is the composition of f1 and f2. f1 is expected to return an array of arguments to pass to f2.

The optional flags hash can contain the pre flag to true which set's f2 to the main function, otherwise f1 is the main function. The returned function's length property is the same as the length property of the main function

var g = f.compose(function addOne(val) {
	return [1, val];
}, function (a, b) {
	return a + b;
});

g(5); // 6
g.length === 1; // true

var g = f.compose(function multiplyTwo(val) {
	return [2, val];
}, function (a, b) {
	return a * b;
}, { pre: true });

g(5); // 10
g.length === 2; // true