Some Array util methods.

array.extras.js

/*!
 * Array Extras, version 1.0
 * Copyright (c) 2012, marlun78
 * MIT License, https://gist.github.com/marlun78/bd0800cf5e8053ba9f83
 * 
 * Depends on type.extras.js
 */
(function(ns){

    // Returns the first index at which a given type can be found in the array, or -1 if it is not present.
    var indexOfType = function (array, type, fromIndex) {
        if (!ns.isArray(array)) { throw new TypeError(/*'indexOfType() first argument must be of type Array.'*/); }
        if (!ns.isString(type)) { throw new TypeError(/*'indexOfType() second argument must be of type String.'*/); }
        type = type.toLowerCase();
        var index = ns.isNumber(fromIndex) ? fromIndex : 0,
            length = array.length;
        while (index < length) {
            if (typeOf(array[index]) === type) { return index; }
            index += 1;
        };
        return -1;
    };

    // Returns the last index at which a given type can be found in the array, or -1 if it is not present.
    var lastIndexOfType = function (array, type, fromIndex) {
        if (!ns.isArray(array)) { throw new TypeError(/*'lastIndexOfType() first argument must be of type Array.'*/); }
        if (!ns.isString(type)) { throw new TypeError(/*'lastIndexOfType() second argument must be of type String.'*/); }
        type = type.toLowerCase();
        var index = ns.isNumber(fromIndex) ? Math.min(array.length, fromIndex) : array.length;
        while (index > 0) {
            index -= 1;
            if (ns.typeOf(array[index]) === type) { return index; }
        };
        return -1;
    };

    // Returns the first element of a given type in the array, or null if none is present.
    ns.elementOfType = function (array, type, fromIndex) {
        var index = indexOfType(array, type, fromIndex);
        return index !== -1 ? array[index] : null;
    };

    // Returns the last element of a given type in the array, or null if none is present.
    ns.lastElementOfType = function (array, type, fromIndex) {
        var index = lastIndexOfType(array, type, fromIndex);
        return index !== -1 ? array[index] : null;
    };

    // Converts an arguments object to a real Array. 
    ns.toArray = function (argumentsObject) {
        return Array.prototype.slice.call(argumentsObject);
    };

    // Expose methods
    ns.indexOfType = indexOfType;
    ns.lastIndexOfType = lastIndexOfType;

}(window.APP));