In jQuery and node.js environments, suppose you have the following:
var object = new Soda().drink("Coke").drink("Pepsi").drink("7Up");
Now let's say I have a list of N drinks and I don't want to hard code this programatically:
var object = new Soda().drink("D1").drink("D2").drink("Dn")...
What is the programatic approach to this problem if I need this to run sequentially and I can't use:
var object = new Soda();
for (var in j){
object.drink(i);
}
The line new Soda().drink("Coke").drink("Pepsi").drink("7Up") implies that .drink() returns a value that by itself is a valid object to call .drink() again with (either the original object, or some other object that encapsulates the modified state).
If that is the case, you could:
var currentDrinkable = object;
for(var drink in drinks) {
currentDrinkable = currentDrinkable.drink(drink)
}
Related
I am trying to be able to make a list of all instances of a Constructor, so I can check if all of these fit criteria in an IF statement
For Example:
function People() {
People.allInstances = [];
People.allInstances.push(this);
}
var Carry = new People();
var Gary = new People();
var Parry = new People();
console.log(People.allInstances);
However, I seem to lose all data except for the last instance I created. How can I make that list/array, and then use that array to test if any of them has a certain property?
The constructor runs every time an instance is constructed with it, but you only want to create an empty array once:
function People() {
People.allInstances.push(this);
}
People.allInstances = [];
I want to create objects in a foreach loop:
I'm starting from this:
data.forEach(function (el) {
var dynamic_var = new Quill(el['editor']);
dynamic_var.on('text-change', logHtmlContent);})
But, dynamic_var is 'overwritten', and I want to remain unique.
I check some html elements, and for each one that I found I want to create a new Object, and execute the Object methods.
In my case the variable get a new object per each iteration, is not a new variable.
Is this what you were looking for?
var quillValueContainer = {};
// ...
data.forEach(function(el) {
quillValueContainer[el] = new Quill(el['editor']);
quillValueContainer[el].on('text-change', logHtmlContent);
});
This will only work if el is a string, or number. Seeing how you are using it like this: el['editor'], makes me thing it's an Object, in which case, you can instead use the indices of the elements.
var quillValueContainer = {}; // [] should also work for indexes
// ...
data.forEach(function(el, index) {
quillValueContainer[index] = new Quill(el['editor']);
quillValueContainer[index].on('text-change', logHtmlContent);
});
Also, I don't know if this is something you need to do, but you can check if the Quill Object has already been initialized and skipping a duplication if it has, by doing:
data.filter(function(el, index){ return !quillValueContainer[index]; }).foreach(...
Or
data.forEach(function(el, index) {
if(quillValueContainer[index]) return;
quillValueContainer[index] = new Quill(el['editor']);
quillValueContainer[index].on('text-change', logHtmlContent);
});
I am trying to create a array with multiple fields in it.
For Example:
var person1 = {firstname:"Bob", lastname:"Smith", middlename:"happy"};
The problem I have is that I have 5000 variables I want to create so it would become:
var person1 = {firstname:"Bob", lastname:"Smith", middlename:"happy"};
var person2 = {firstname:"John", lastname:"Jones", middlename:"Long"};
..
var person5000 = {firstname:"Jim", lastname:"Cook", middlename:"Shorty"};
I think it would be silly to have 5000 lines of code to declare the variables.
So I want to be able to declare the variables on page load and then later assign the values to each.
I was trying to do this using the following code but I am guessing I am doing something wrong.
(I am loading some dummy data into the variables for testing)
<!DOCTYPE html>
<html>
<body>
<script>
var person = new Array (firstName:"", lastName:"", middleName:"");
for (var i = 0; i < 5000; ++i) {
person[i] = {firstName:"First"+i, lastName:"Last"+i, middlename:"Middle"+i};
}
alert(person1["firstName"]); // should alert First1
alert(person6["lastname"]); // should alert Last6
</script>
</body>
</html>
I was hoping to later in my code set the value using:
(I am pretty sure this code should work, but can't test it since I can't declare the variables correctly)
person1[firstname] = "Terry"; // should replace First1 with Terry
And then to receive a value using:
alert(person1[firstname]); // should alert Terry since it was changed
Anyone know what is wrong with my code since it's not returning the value ?
I am guessing I am declaring the variables wrong? If so how should I declare them ?
You appear to be confused about the difference between arrays and objects in Javascript. Arrays have numeric indexes, objects have named properties. So the initialization
new Array(firstName:"", lastName:"", middleName:"");
makes no sense. Not to mention, it's not valid Javascript syntax; property: value pairs can only be used in object literals, not in argument lists. If you use new Array(...), the argument should either be a single number, which is the size of the array to allocate, or a list of initial array element (with no property: prefixes. But the preferred way to create a new array is simply with the [] literal for an empty array; it will grow as necessary when you assign to it.
When you create an array, you don't get separate variables for each element. You access them using array[n] notation.
// Create an empty array
var person = [];
// Fill up the array
for (var i = 0; i < 5000; ++i) {
person[i] = {firstName:"First"+i, lastName:"Last"+i, middlename:"Middle"+i};
}
// Access elements
alert(person[1].firstName);
alert(person[6].middleName);
// Change elements
person[1].firstName = "Terry";
I believe this should work as you intended:
var person = new Array();
for (var i = 0; i < 5000; ++i) {
person[i] = {firstName:"First"+i, lastName:"Last"+i, middleName:"Middle"+i};
}
alert(person[1]["firstName"]);
alert(person[6]["lastName"]);
As pointed out by others, the person array is filled with objects, not arrays. You can use either property or associative array syntax with them.
Hi I am new with javascript, there is a problem that is driving me crazy:
what is the difference between an object staticly declared as this one :
{$or:[{tc_clpar_id:4,tc_par_id:{$in:[79,80]}},{tc_clpar_id:5,tc_par_id:{$in:[105,106]}}]}
and an object costruct at run-time, with this function:
function buildQuery(self,setting,query){
var query = {$or:[]};
cl = 'tc_cl'+self.family+'_id';
att ='tc_'+self.family+'_id';
keys = Object.keys(setting);
for( var k=0;k<keys.length;k++){
ch = keys[k];
var q = {};
q[cl] = ch;
q[att] = {$in:setting[ch]};
query.$or.push(q);
}
return query;
this object is used as query for the node-mongodb-native driver, the first one works, the object return by the function in correct, I checked the two object with assert.deepEqual, there are no errors, but using the produced object I get an empty resultset, I do not have any clue about the problem, I thought maybe something strange with the scope as the function is a method of another object, or maybe with the garbage collector.
I am a newbie in JS. Here is my code and I believe it should work... but it doesn't.
var pop = new Array();
pop['la'] = new Array('nt','gb','te');
pop['sa'] = new Array('nt','gb');
pop['ha'] = new Array('pc','pa');
var _ecpop="la";
for (var i = 0; i < pop[_ecpop].length; i++)
{
document.write(pop[_ecpop][i]);
}
I just do not know any alternate way to have a map of vectors of a string.
Thanks,
Amir.
That's not an Array, but a Javascript Object, containing Arrays in it's properties. You can use Object and Array literals for that. The advantage is that your code looks much cleaner. There are seldom reasons to use new Array or new Object in javascript code (see for example this SO Question).
var pop = {
la: ['nt','gb','te'],
sa: ['nt','gb'],
ha: ['pc','pa']
}
now you can use
for (var i = 0; i < pop.la.length; i++) {
console.log(pop.la[i]);
}
if a property label is stored in a variable (like you _ecpop), you can use bracket notiation to retrieve it's value:
var laArr = pop[_ecpop];
for (var i = 0; i < laArr.length; i++) {
console.log(laArr[i]);
}
The other way around you can assign a label to an Object:
var _ecpop = 'la';
pop[_ecpop] = ['nt','gb','te'];
document.write is not the preferred way to put things on your page. It's better and just as easy to use some element with an id, and write output to it using innerHTML, for example
document.getElementById('myOutput').innerHTML = '[some output here]';
In javascript, an array can only have numeric indexes, if you want to use textual indexes, you should use object instead.
var pop = new Object();
or
var pop = {};
and then:
pop['la'] = new Array('nt','gb','te');
However, as an object is not an array, it has no length member, but just as an array you can use the for..in to go through all of its values.
Using document.write is not a good choice as it only works during the document loading, not after it. Try to use text nodes or innerhtml instead.