node-cond/index.js

lisp "cond" special form realization for js

var isFn = (some) => typeof some === "function",
    
    cond = function (...args) {
        return loopByArgs(args, false);
    };

    cond.all = function (...args) {
        return loopByArgs(args, true);
    };

    cond.doif = function (Then, Else) {
        return function (condition) {
            return cond(
                condition, returnValue(Then, condition),
                    returnValue(Else, condition) )
        }
    };

module.exports = cond;

function loopByArgs(args, all) {
    var i = 0,
        argsLen = args.length,
        defaultValue = argsLen % 2 ? args.pop() : undefined,
        lastValue;
    for(; i < argsLen; i += 2) {
        let condition = args[i];
        if(condition) {
            let returnedValue = args[i+1];
            if(all) {
                lastValue = returnValue(returnedValue, condition)
            } else {
                return returnValue(returnedValue, condition);
            }
        }
    }
    return defaultValue ? returnValue(defaultValue) : lastValue;
};

function returnValue(value, condition) {
    return isFn(value) ? value(condition) : value;
};