I was messing with some js on codecadamy and got a bit sidetracked trying to make something work.
In essence I was creating a few objects that are loaded into a controller object and set as properties of it with two functions that print the properties and compare a string to the name property of each object in the controller.
I noticed I can do it if I make the objects in the prototype style and specify a normal function to handle setting the properties like so:
var friends = {};
friends.setUp = function() {
this.friends = [];
for(var i in arguments) {
arguments[i].setUp();
this.friends.push(arguments[i]);
}
};
friends.list = function() {
for(var i in this.friends) {
console.log(this.friends[i]);
}
};
friends.search = function(name) {
for(var i in this.friends) {
if(this.friends[i].firstName === name) {
return this.friends[i];
}
}
};
var bill = {};
bill.setUp = function() {
this.firstName = "Bill";
this.lastName = "Gates";
this.number = "(206) 555-5555";
this.address = ['One Microsoft Way','Redmond','WA','98052'];
};
var steve = {};
steve.setUp = function() {
this.firstName = "Steve";
this.lastName = "Jobs";
this.number = "(206) 555-5555";
this.address = ['1 Infinite Loop','Cupertino','CA','95014'];
};
var mike = {};
mike.setUp = function() {
this.firstname = "Mike";
this.lastname = "Ryd";
this.number = "(800) 555-5555";
this.address = ['redacted'];
};
friends.setUp(bill, steve, mike);
friends.list();
var result = friends.search("Steve");
console.log(result);
However if I do it with constructors It does not work, example:
function bill() {
this.firstName = "Bill";
this.lastName = "Gates";
this.number = "(206) 555-5555";
this.address = ['One Microsoft Way','Redmond','WA','98052'];
};
function steve() {
this.firstName = "Steve";
this.lastName = "Jobs";
this.number = "(206) 555-5555";
this.address = ['1 Infinite Loop','Cupertino','CA','95014'];
};
function mike() {
this.firstname = "Mike";
this.lastname = "Ryd";
this.number = "(800) 555-5555";
this.address = ['redacted'];
};
function friends() {
this.friends = [];
for(var i in arguments) {
this.friends.push(arguments[i]);
}
};
friends.list = function() {
for(var i in this.friends) {
console.log(this.friends[i]);
}
};
friends.search = function(name) {
for(var i in this.friends) {
if(this.friends[i].firstName === name) {
return this.friends[i];
}
}
};
var bill = new bill();
var steve = new steve();
var mike = new mike();
var friends = new friends(bill, steve, mike);
friends.list();
var result = friends.search("Steve");
console.log(result);
I was wondering if this is a limitation of using constructors or am I messing up the syntax somewhere? Thank you!
This doesn't appear to have anything to do with constructors with an unknown number of arguments, but rather you are not assigning methods on your objects appropriately. They need to be put on the prototype so that they will be inherited by all objects that are created by this particular constructor. So in your code, these:
friends.list = function() {...}
friends.search = function() {...}
needs to be changed to:
friends.prototype.list = function() {...}
friends.prototype.search = function() {...}
Like this:
friends.prototype.list = function() {
for(var i = 0; i < this.friends.length; i++) {
console.log(this.friends[i]);
}
};
friends.prototype.search = function(name) {
for(var i = 0; i < this.friends.length; i++) {
if(this.friends[i].firstName === name) {
return this.friends[i];
}
}
};
Then, this code should work fine:
var bill = new bill();
var steve = new steve();
var mike = new mike();
var friends = new friends(bill, steve, mike);
friends.list();
var result = friends.search("Steve");
console.log(result);
And, then the code works as you would expect here: http://jsfiddle.net/jfriend00/ba4me8ua/
FYI, you'll noticed that I changed the way you iterate through the arguments object items to be more array-like and avoid any chance of getting any non-numeric properties in the iteration.
Related
so I would like to access an an array i created in a previous function. and then in id1,id2,id3, i would Like to create a new property and give that property a value. I thought I have an idea of what I should do but what Im doing is not working. I get the error IdArray is undefined.
HTML:
<p id="show_me"></p>
<button onclick="ObjectArray()">click me</button>
<p id="added"></p>
<button onclick="Added()">Add</button>
javascript previous function:
var ObjectArray = function() {
// object literal
var id1 = {
firstName: "John",
lastName: "Doe",
id: "12345"
};
// keyword new
var id2 = new Object;
id2.firstName = "Adam";
id2.lastName = "Bakely";
id2.id = "abcdef";
// object constructor
function employee(first, last, id) {
this.firstName = first;
this.lastName = last;
this.id = id;
}
var id3 = new employee("Dallas", "Star", "abc123");
//create an array
var IdArray = [id1, id2, id3];
}
javascript new function:
function Added(IdArray, sex){
IdArray.push({sex : sex})
IdArray[0].sex = "male";
document.getElementById("added").innerHTML = IdArray[0];
}
im lost, so how do I access the array from the previous function and add to it?
You do not have access to variables in other functions, you can however access variable declared above your functions. Your real problem is a failure to understand Constructors, which will greatly benefit you in the future. Check this out:
function Employee(id, firstName, lastName, middleName){
this.id = id; this.firstName = firstName; this.lastName = lastName;
this.middleName = middleName;
this.notes = [];
this.getFullName = function(){
var mn = this.middleName ? ' '+this.middleName : '';
return this.firstName+mn+' '+this.lastName;
}
this.createNote = function(note){
this.notes.push(note);
return this;
}
this.getNotesString = function(delimiter){
return this.notes.join(delimiter);
}
}
var employee1 = new Employee('abc123', 'Joe', 'Schmoe');
employee1.createNote('Note You Want to Store.');
employee1.createNote('Just Another Test Note.');
var employee2 = new Employee('def456', employee1.firstName, 'Smith', 'Walter'); // notice how you access the other instance firstName
console.log(employee1.getFullName());
console.log(employee1.getNotesString('|'));
console.log(employee2.getFullName());
console.log(employee2.createNote('Note 1').createNote('Note 2').createNote('Note 3').getNotesString('|')); // by returning `this` you can access other methods in the same Constructor
You need to either save the IdArray or to return it:
var IdArray;
var ObjectArray = function() {
// object literal
var id1 = {
firstName: "John",
lastName: "Doe",
id: "12345"
};
// keyword new
var id2 = new Object;
id2.firstName = "Adam";
id2.lastName = "Bakely";
id2.id = "abcdef";
// object constructor
function employee(first, last, id) {
this.firstName = first;
this.lastName = last;
this.id = id;
}
var id3 = new employee("Dallas", "Star", "abc123");
//create an array
IdArray = [id1, id2, id3]; //removed the var keyword, so I am using the global variable
}
and then use it.
notice I removed the var keyword so I am using the global IdArray.
The variable IdArray was created inside the function, so it expires when the function ends. If you add the line
var IdArray;
before your first function that will make it global instead. Then reference to IdArray inside either function will refer to the same variable.
I added the IdArray as a property of the window object to give it global scope:
var ObjectArray = function() {
// object literal
var id1 = {
firstName: "John",
lastName: "Doe",
id: "12345"
};
// keyword new
var id2 = new Object;
id2.firstName = "Adam";
id2.lastName = "Bakely";
id2.id = "abcdef";
// object constructor
function employee(first, last, id) {
this.firstName = first;
this.lastName = last;
this.id = id;
}
var id3 = new employee("Dallas", "Star", "abc123");
//create an array
window.IdArray = [id1, id2, id3];
}
I'm building an array dynamically in a test angular app. Basically I have a scope function that generates an array of people and returns the array and I have an ng-repeat on the array. The array is not displaying but I'm not getting any errors in the console either, so idk what's up:
am I calling the getPerson function correctly? If there's a better way to do this do let me know.
heres the fiddle as well
$scope.person = {
firstname: "",
lastname: "",
isActive: true,
fullname: function() {
var personobject;
personobject = $scope.person;
return personobject.firstname
+ " "
+ personobject.lastname;
}
};
$scope.people = function() {
var pplArray = [];
var firstnames = ['abdul','mahmud','gasser','ibtihaj','abudi'];
var lastnames = ['ahmad','samrai','badawi','jasim','ahmad'];
var actives = [true,true,false,true,false];
for (var i = 0; i < firstnames.length; i++) {
pplArray[i] = getPerson(firstnames[i], lastnames[i], actives[i]);
}
return pplArray;
};
$scope.getPerson = function(first, last, active) {
var newPerson = $scope.person;
newPerson.firstname = first;
newPerson.lastname = last;
newPerson.isActive = active;
return newPerson;
};
I've updated your fiddle here : https://jsfiddle.net/7j2khgbj/2/
var myapp = angular.module("myapp", []);
myapp.controller('appCont', function($scope) {
var Person = function(){
this.firstname = "";
this.lastname = "";
this.isActive = true;
};
Person.prototype.fullname = function() {
return this.firstname
+ " "
+ this.lastname;
};
var getPerson = function(first, last, active) {
var newPerson = new Person();
newPerson.firstname = first;
newPerson.lastname = last;
newPerson.isActive = active;
return newPerson;
};
$scope.addPerson = function() {
$scope.people.push({
firstname: $scope.person.firstname,
lastname: $scope.person.lastname
});
$scope.person.firstname = '';
$scope.person.lastname = '';
};
$scope.people = (function() {
var pplArray = [];
var firstnames = ['abdul','mahmud','gasser','ibtihaj','abudi'];
var lastnames = ['ahmad','samrai','badawi','jasim','ahmad'];
var actives = [true,true,false,true,false];
for (var i = 0; i < firstnames.length; i++) {
pplArray[i] = getPerson(firstnames[i], lastnames[i], actives[i]);
}
return pplArray;
})();
/*$scope.people = [
{firstname: 'abdul', lastname: 'ahmad'},
{firstname: 'mahmud', lastname: 'samrai'},
{firstname: 'gasser', lastname: 'badawi'},
{firstname: 'ibtihaj', lastname: 'jasim'},
{firstname: 'abudi', lastname: 'ahmad'},
{firstname: 'ahmad', lastname: 'jasim'},
{firstname: 'abdul', lastname: 'samrai'}
];*/
});
Some problems I saw:
1) $scope.people was a function, not an array (so I simply executed it and saved the result)
2) you were always overwriting the person (you need a Person class that creates new instances for the array element, not overwrite the same instance with new data - that way you'll get the same thing in all the array elements)
3) on $scope you should put things that need to be accessible from the view. Helper functions can just be local in the controller (if you don't want them as services, although as services they are reusable)
4) track by on ng-repeat (in case of duplicate keys)
I am working on a project whereby i have noticed there are multiple references to the same objects in different areas. But i have been reading on mixins and just prototypal inheritance but not sure which one to follow:
So my current objects look like below but i need for product to inherit the base class including the function which is used everytime.
var base = function() {
this.id = 0;
this.refererer = null;
this.getCurrency = function() {
return "US"
}
}
var product = function() {
this.name = "";
this.description = "";
}
How can i implement the above to use either mixins or prototypal inheritance?
var base = function() {
this.id = 0;
this.refererer = null;
this.getCurrency = function() {
return "US"
}
}
var product = function() {
this.name = "";
this.description = "";
}
product.prototype = new base(); // this will do the inheritance trick
product.prototype.constructor = product;
var proObj = new product();
alert(proObj.id); // 0 base class property "id"
I'm making a digital library with three classes: Library, Shelf & Book. Shelves have their contents as an array of books. Books have two methods, enshelf and unshelf. When a book gets unshelfed it's supposed to set delete the instance of itself from the shelf it's on and then set it's location property to null. How can I modify the shelf it's sitting on? In the constructor if I change this.location, it will just give that property a new value instead of modifying the variable it points to. I feel like this is really simple and I'm overlooking something super basic.
var _ = require('lodash');
//books
var oldMan = new Book("Old Man and the Sea", "Ernest Hemingway", 0684801221);
var grapes = new Book("The Grapes of Wrath", "John Steinbeck", 0241952476);
var diamondAge = new Book("The Diamond Age", "Neal Stephenson", 0324249248);
//shelves
var shelf0 = new Shelf(0);
var shelf1 = new Shelf(1);
//libraries
var myLibrary = new Library([shelf0, shelf1], "123 Fake Street");
//these need to accept an unlimited amount of each
function Library(shelves, address) {
this.shelves = shelves; //shelves is an array
this.address = address;
this.getAllBooks = function() {
console.log("Here are all the books in the library: ");
for (var i = 0; i < this.shelves.length; i++) {
console.log("Shelf number " + i + ": ");
for (var j = 0; j < this.shelves[i].contents.length; j++) {
console.log(this.shelves[i].contents[j].name);
}
}
}
}
function Shelf(id) {
this.id = id;
this.contents = [];
}
function Book(name, author, isbn) {
this.name = name;
this.author = author;
this.isbn = isbn;
this.location = null;
this.enshelf = function(newLocation) {
this.location = newLocation;
newLocation.contents.push(this);
}
this.unshelf = function() {
_.without(this.location, this.name); //this doesn't work
this.location = null;
}
}
console.log("Welcome to Digital Library 0.1!");
oldMan.enshelf(shelf1);
myLibrary.getAllBooks();
oldMan.unshelf();
myLibrary.getAllBooks();
Small issue with your unshelf method, easily remedied:
this.unshelf = function() {
this.location.contents =
_.without(this.location.contents, this);
this.location = null;
}
Consider, however, that shelf and unshelf should be methods of Shelf, and not of Book. Also, if you must have this method, surround it with a guard, like so:
this.unshelf = function() {
if (this.location) {
this.location.contents =
_.without(this.location.contents, this);
this.location = null;
}
}
Couple of small issues:
without works on arrays and returns a copy of the array with the elements removed - the original is untouched. So you need to pass location.contents instead of just location and reassign it back to location.contents.
Also you add the whole book to the Shelf, then try to remove it by name, so it doesn't match and get removed. So just pass this to without:
this.unshelf = function() {
if (this.location) {
this.location.contents = _.without(this.location.contents, this);
this.location = null;
}
}
Code snippet 1:
<script>
function Person(lastName, firstName){
this.lastName = lastName;
this.firstName = firstName;
}
var DnnyGdmn = new Person("Goodman","Danny");
var DvdFlngn = new Person("Flanagan","David");
function Book(title, pages, price){
this.title = title;
this.pages = pages;
this.price = price;
this.authors = new Array(arguments.length-3);
console.log(arguments);
for(i = 0; i < arguments.length - 3; i++){
this.authors[i] = arguments[i + 3];
}
}
var JavaNut = new Book("Java Foundation Classes in a Nutshell", 731, 29.95, DvdFlngn);
var JSTDR = new Book("Javascript: The Definitive Guide (3rd Edition)", 776, 39.95, DvdFlngn);
</script>
In Firefox firebug->console->all, I see:
["Java Foundation Classes in a Nutshell", 731, 29.95, Person { lastName="Flanagan", firstName="David"}]
["Javascript: The Definitive Guide (3rd Edition)", 776, 39.95, Person { lastName="Flanagan", firstName="David"}]
Code snippet 2:
<script>
function Person(lastName, firstName){
this.lastName = lastName;
this.firstName = firstName;
}
var DnnyGdmn = new Person("Goodman","Danny");
var DvdFlngn = new Person("Flanagan","David");
</script>
In Firefox firebug->console->all, it does not show anything.
Question:
Both code snippets do the same thing, creating an instance of a certain object, but why does 1 write something to console, while code 2 does not?
In the codes 1, you have this:
console.log(arguments);
This can be found here:
...
this.pages = pages;
this.price = price;
this.authors = new Array(arguments.length-3); console.log(arguments);
for(i=0;i<arguments.length-3;i++){
this.authors[i] = arguments[i+3];
}
...
This code writes the arguments value to the console. Since the code is not present in the codes 2, it doesn't output anything in the console.