Javascripts - Ian Link

bind_from_json.js

/*------------------------------------------------------------------------------------
 *
 *  Bind from JSON - uses JSON to set up UI bindings. Utilizes jquery's 'bind'
 *  
 *  Usage:
 *  Supply JSON file formatted like this:
 *      var json = [{
 *          'selector' : '#id',
 *          'bind_to' : 'click',
 *          'func' : [
 *				func1,
 *				func2
 *			]
 *      }];
 *
 *	Call the function:
 *		jsUtil.bind_from_json(json)
 *	
 *  Note that you can include any valid jquery selector or combination of selectors
 *  
 *  Changelog:
 *
 *  Version 0.3: Better typechecking
 *  
 *	Version 0.2: Added support for binding to multiple functions
 *		- Better error reporting for type-checking errors
 *  
 *	Version 0.1: Initial commit
 *  
 -----------------------------------------------------------------------------------*/
if (typeof jsUtil === 'undefined'){
    var jsUtil = {};
}

jsUtil.bind_from_json = function(json){
    "use strict";
    if(typeof json == 'undefined') return 'No json supplied'
    for (var i = 0; i < json.length; i++){
	if (typeof json[i].selector !== 'string'){
		throw "Error in supplied JSON at index "+ i + ". Expects 'Selector' as String";
	}
	if (typeof json[i].bind_to !== 'string'){
		throw "Error in supplied JSON at index "+ i + ". Expects 'Bind_to as String";
	}
        if (json[i].hasOwnProperty('func')) {
            if (typeof json[i].func === 'object') {
                for (var j = 0; j < json[i].func.length; j++){
                    if (typeof json[i].func[j] !== 'function'){
                        throw "Error in supplied JSON at index " + i + ". Expects 'func' to be functions. The " + j + "th entry for 'functions' is not a function";
                    }
                    $(json[i].selector).bind(json[i].bind_to, json[i].func[j]);
                }
            }
            else {
                if (typeof json[i].func !== 'function'){
                    throw "Error in supplied JSON at index " + i + ". Expects 'func' to be a function.";
                }
                $(json[i].selector).bind(json[i].bind_to, json[i].func);
            }
        }
        else throw 'Has no functions to bind to!'
    }
}

js_command_history.js

// This class is basically the undo & redo structure of a command pattern - it keeps track of all undo-able commands
// Each undo-able command would have an execute() and an unexecute() command. 
// The user will call this function to undo / redo commands. Note the specific use of garbage collection to avoid a memory leak

var history = (function() {
    var iterator = -1;   //marks the "present" command, the last command issued
    var end = -1;
    var start = -1;
    var max_size = 3;
    var command_history = [];   //array to store all the commands
    return {
        //TODO if this method isnt fast enough, I can try a linkedlist or an array shift
        add : function( command ) {
            if( end >= (max_size - 1) ) {    //assuming the client wants max_size in terms of '# of elements' not 'size of base-0 array'
                command_history[start] = undefined;     //we need to let the unused data (the oldest commands) get garbage collected
                start++, end++; //move the array onwards so we can ignore + safely delete the oldest command in history
                iterator = end; //move the iterator to the front when a new command is added
                command_history.push(command);
                console.log('trying to remove earliest command');
            }
            else {
                end++;
                if (start == -1) start = 0;
                iterator = end;
                command_history.push(command);
            }
        },
        undo : function() {
            if (iterator == (start-1)) return null
            else {
                if (iterator == end + 1) iterator = end;
                if (iterator >= start) {
                    command_history[iterator].unexecute();
                    iterator--;
                    console.log("iter:" + iterator);
                }
            }
        },
        redo : function() {
            if (iterator == (end+1)) return null
            else {
                if (iterator <= end) {
                    iterator++;
                }
                if (iterator <= end) {
                    command_history[iterator].execute();
                }
            }
        },
        logger : function() {
            console.log("start: " + start + " end: " + end);
        }
    }
})();

make_sticky.js

// This function makes it easy to keep a div on top of the screen, no matter where the user scrolls
var make_sticky = function(selector, location, threshold){
    (function(){ // the extra closure is for these variables below
        var former_position = $(selector).css('position');
        var former_top = $(selector).css('top');
        $(window).scroll(function () {
                if($(this).scrollTop() > threshold){
                    $(selector).css({
                        "position" : "fixed",
                        "top" : '0px'
                    });
                }
                if ($(this).scrollTop() < threshold){
                    $(selector).css({
                        "position" : former_position,
                        "top" : former_top
                    });
                }
            });
    })();
}

type_checker.js

/*
Usage:

var provided = {
    arg1 : "arg1",
    arg1 : 2
}

var should_be = {
    arg1 : "string",
    arg2 : "object"
}

This would throw an error for arg2 because it is the wrong type.
 */

var Type_checker = function(){
    if(this instanceof Type_checker){
        var errors = [];
        this.check = function(check_me, should_be, extra_error_message){
            $.each(check_me, function(key, value) {
                if(typeof value !== should_be[key]){
                    var should_be_val = should_be[key];
                    var error = key + ' is a(n) ' + typeof value + ' when it should be a(n) ' + should_be_val;
                    error = error + '. ' + extra_error_message;
                    errors.push(error);
                }
            });
            return errors;
        }
        this.log_errors = function(){
            $.each(errors, function(key, value){
               console.log(value);
            });
        }
    }
    else return new Type_checker()
}