compose_only.js

(function (global) {
    var cache = {};

    function c(n) {
        if (n < 1) {
            return new Function;
        }
        var i;
        var params = "";
        var vars = "  return function () {" + "\n";
        var body = "    return _0;" + "\n" + "  };";
        for (i = 0; i < n; i += 1) {
            params += i ? (", fn" + i) : "fn" + i;
        }
        vars += "    var _" + --i + " = fn" + i + ".apply(this, arguments);" + "\n";
        while (i--) {
            vars += "    var _" + i + " = fn" + i + ".call(this, _" + (i + 1) + ");" + "\n"
        }
        return Function(params, vars + body);
    };
    
    global.compose = function (/*fn1[, fn2[, fn3...]]*/) {
        var n = arguments.length;
        return (cache[n] = cache[n] || c(n)).apply(this, arguments);
    };
}(this));

compose_only_examples.js

function slice(obj) {
    return Array.prototype.slice.call(obj, 0);
} 
function makeArray(obj) {
    if (obj === null || obj === undefined) {
        return [];
    }
    if (obj instanceof Array) {
        return obj;
    }
    if (obj instanceof Object && "length" in obj && "0" in obj) {
        return slice(obj);
    }
    return [obj];
}
var fixedArr = [1,2,3];
function fixed() {
    return fixedArr;
}
function makeUnary(arg) {
    if (arguments.length > 1) {
        return arguments;
    }
    return arg;
}
//compose slice and makeArray passing fixed as a parameter
console.assert(JSON.stringify(compose(slice, makeArray)(fixed())) === "[1,2,3]");
console.assert(compose(slice, makeArray)(fixed()) !== fixed());
//compose slice, makeArray, and fixed
console.assert(JSON.stringify(compose(slice, makeArray, fixed)()) === "[1,2,3]");
console.assert(compose(slice, makeArray, fixed)() !== fixed());
//compose slice, makeArray, and makeUnary so any signature will produce a list
var list = compose(slice, makeArray, makeUnary);
var testlist = compose(JSON.stringify, slice, makeArray, makeUnary);
console.assert(JSON.stringify(list(1)) === "[1]");
console.assert(testlist(1) === "[1]");
console.assert(JSON.stringify(list(1,2)) === "[1,2]");
console.assert(testlist(1,2) === "[1,2]");
console.assert(JSON.stringify(list([1,2])) === "[1,2]");
console.assert(testlist([1,2]) === "[1,2]");
console.assert(JSON.stringify(list({0:1,1:2,length:2})) === "[1,2]");
console.assert(testlist({0:1,1:2,length:2}) === "[1,2]");