fixa/lib/fixa.js

Fixa (from Fix Arguments) is a Javascript Library to fix the number of arguments returned on callbacks.

/**
 * Takes a function (usually callbacks), and fix the number of arguments that it returns on execution to N arguments.
 * If the original function had return more parameters, they are ignored and just firsts N arguments are returned.
 * If the original function had return less parameters, all of them are returned along with null values until complete N arguments.
 *
 * @param callback
 * @param N
 * @returns {Function}
 * @constructor
 */
var Fixa = function Fixa(callback, N) {
    return function executeCallback() {
        var newArguments = [];
        for (var i = 0; i < N; i++) {
            newArguments.push(arguments[i] || null);
        }
        // Send limited arguments
        callback.apply(this, newArguments);
    }
};

/**
 * Fix the number of arguments returned in a callback to N.
 *
 * @param N The number of arguments to return in callback
 * @returns {*}
 */
Function.prototype.fixa = function fixa(N) {
    var originalFunction = this;
    return function executeFunction() {
        var callback = arguments[arguments.length - 1];

        if (callback && ({}).toString.call(callback) === '[object Function]') {
            var originalArgs = arguments;
            // Rewrite callback
            originalArgs[originalArgs.length - 1] = Fixa(callback, N);

            originalFunction.apply(this, originalArgs);
        } else {
            // No callback sent, return results
            return originalFunction.apply(this, arguments);
        }
    }
};

/**
 * Synonym for fixa function
 *
 * @returns {*}
 */
Function.prototype.fixArguments = function fixArguments(N) {
    return this.fixa(N).apply(this, arguments);
};

/**
 * Make callback returns no arguments.
 *
 * @returns {*}
 */
Function.prototype.noArgs = function noArgs() {
    return this.fixa(0).apply(this, arguments);
};

/**
 * Fix the number of arguments returned in a callback to 1 argument.
 *
 * @returns {*}
 */
Function.prototype.oneArg = function oneArg() {
    return this.fixa(1).apply(this, arguments);
};

/**
 * Fix the number of arguments returned in a callback to 2 arguments.
 *
 * @returns {*}
 */
Function.prototype.twoArgs = function twoArgs() {
    return this.fixa(2).apply(this, arguments);
};

/**
 * Fix the number of arguments returned in a callback to 3 arguments.
 *
 * @returns {*}
 */
Function.prototype.threeArgs = function threeArgs() {
    return this.fixa(3).apply(this, arguments);
};

/**
 * Fix the number of arguments returned in a callback to 4 arguments.
 *
 * @returns {*}
 */
Function.prototype.fourArgs = function fourArgs() {
    return this.fixa(4).apply(this, arguments);
};

module.exports = Fixa;