So I have a bunch of values I need to convert to new values. Basically with a legend. It'll make sense in a second. So far, I've been using associative arrays, or in the context of javascript, objects as my legend.
My use is applicable to individual strings, arrays as I have blow, or objects.
var legend = {
"html": "html5",
"css2": "css3",
"javascript": "jquery"
}
var old_array = new Array("html", "css2", "javascript");
var new_array = [];
max = old_array.length;
// loop through values in original array
for(i=0;i<max;i++){
for(var val in legend){
// looping through values in legend. If match, convert
if(old_array[i] === val){
new_array[i] = legend[val];
}
}
}
console.log(new_array);
document.write(new_array);
If you paste that into firebug or jsfiddle, it'll show a new array with the converted values.
I decided on object/associative array as my legend because it's easy to expand in case new values need to be converted. I think it's pretty robust. And it works for converting an individual string, an array as shown above, or an object, either the keys or the values.
For converting values, is it the best method? Any considerations? For php, as it's the only other language I use regularly, would the same concept, with an associative array, also be used?
Thanks so much for your help and advice!
Cheers!
You're not using the power of the object as there is no reason to loop through the object. It already has keys that you can just lookup directly like this:
var legend = {
"html": "html5",
"css2": "css3",
"javascript": "jquery"
}
var old_array = new Array("html", "css2", "javascript");
var new_array = [];
max = old_array.length;
// loop through values in original array
for(var i=0;i<max;i++){
// see if array value is a key in the legend object
if ([old_array[i] in legend) {
new_array.push(legend[old_array[i]]);
}
}
console.log(new_array);
document.write(new_array);
I also changed it to use new_array.push() so you don't end up with an array with some undefined values, but I'm not really sure what type of end result you're trying to end up with.
Related
Struggling with some javascript array manipulation/updating. Hope someone could help.
I have an array:
array('saved_designs'=array());
Javascript JSON version:
{"saved_design":{}}
I will be adding a label, and associated array data:
array("saved_designs"=array('label'=array('class'='somecssclass',styles=array(ill add more assoc elements here),'hover'=array(ill add more assoc elements here))))
Javascript version:
{"saved_designs":{"label":{"class":"someclass","style":[],"hover":[]}}}
I want to be able to append/modify this array. If 'label' already defined...then cycle through the sub data for that element...and update. If 'label' doesnt exist..then append a new data set to the 'saved_designs' array element.
So, if label is not defined, add the following to the 'saved_designs' element:
array('label2' = array('class'=>'someclass2',styles=array(),'hover=>array()')
Things arent quite working out as i expect. Im unsure of the javascript notation of [], and {} and the differences.
Probably going to need to discuss this as answers are provided....but heres some code i have at the moment to achive this:
//saveLabel = label the user chose for this "design"
if(isUnique == 0){//update
//ask user if want to overwrite design styles for the specified html element
if (confirm("Their is already a design with that label ("+saveLabel+"). Overwrite this designs data for the given element/styles?")) {
currentDesigns["saved_designs"][saveLabel]["class"] = saveClass;
//edit other subdata here...
}
}else{//create new
var newDesign = [];
newDesign[saveLabel] = [];
newDesign[saveLabel]["class"] = saveClass;
newDesign[saveLabel]["style"] = [];
newDesign[saveLabel]["hover"] = [];
currentDesigns["saved_designs"].push(newDesign);//gives error..push is not defined
}
jQuery("#'.$elementId.'").val(JSON.stringify(currentDesigns));
thanks in advance. Hope this is clear. Ill update accordingly based on questions and comments.
Shaun
It can be a bit confusing. JavaScript objects look a lot like a map or a dictionary from other languages. You can iterate over them and access their properties with object['property_name'].
Thus the difference between a property and a string index doesn't really exist. That looks like php you are creating. It's called an array there, but the fact that you are identifying values by a string means it is going to be serialized into an object in javascript.
var thing = {"saved_designs":{"label":{"class":"someclass","style":[],"hover":[]}}}
thing.saved_designs.label is the same thing as thing["saved_designs"]["label"].
In javascript an array is a list that can only be accessed by integer indices. Arrays don't have explicit keys and can be defined:
var stuff = ['label', 24, anObject]
So you see the error you are getting about 'push not defined' is because you aren't working on an array as far as javascript is concerned.
currentDesigns["saved_designs"] == currentDesigns.saved_designs
When you have an object, and you want a new key/value pair (i.e. property) you don't need a special function to add. Just define the key and the value:
**currentDesigns.saved_designs['key'] = newDesign;**
If you have a different label for every design (which is what it looks like) key is that label (a string).
Also when you were defining the new design this is what javascript interprets:
var newDesign = [];
newDesign is an array. It has n number of elements accessed by integers indices.
newDesign[saveLabel] = [];
Since newDesign is a an array saveLabel should be an numerical index. The value for that index is another array.
newDesign[saveLabel]["class"] = saveClass;
newDesign[saveLabel]["style"] = [];
newDesign[saveLabel]["hover"] = [];
Here explicitly you show that you are trying to use an array as objects. Arrays do not support ['string_key']
This might very well 'work' but only because in javascript arrays are objects and there is no rule that says you can't add properties to objects at will. However all these [] are not helping you at all.
var newDesign = {label: "the label", class: saveClass};
is probably what you are looking for.
This is the array:
{"C8_235550":
{"listing":"aut,C8_235550_220144650654"},
"C8_231252":
{"listing":"aut,C8_231252_220144650654"}}
It was fetched with a GET request from a Firebase database using Google Apps Script.
var optList = {"method" : "get"};
var rsltList = UrlFetchApp.fetch("https://dbName.firebaseio.com/KeyName/.json", optList );
var varUrList = rsltList.getContentText();
Notice the .getContentText() method.
I'm assuming that the array is now just a string of characters? I don't know.
When I loop over the returned data, every single character is getting pushed, and the JavaScript code will not find key/value pairs.
This is the FOR LOOP:
dataObj = The Array Shown At Top of Post;
var val = dataObj;
var out = [];
var someObject = val[0];
for (var i in someObject) {
if (someObject.hasOwnProperty(i)) {
out.push(someObject[i]);
};
};
The output from the for loop looks like this:
{,",C,8,_,2,3,5,5,5,0,",:,{,",l,i,s,t,i,n,g,",:,",a,u,t,,,C,8,_,2,3,5,5,5,0,_,2,2,0,1,4,4,6,5,0,6,5,4,",},,,",C,8,_,2,3,1,2,5,2,",:,{,",l,i,s,t,i,n,g,",:,",a,u,t,,,C,8,_,2,3,1,2,5,2,_,2,2,0,1,4,4,6,5,0,6,5,4,",},}
I'm wondering if the array got converted to a string, and is no longer recognized as an array, but just a string of characters. But I don't know enough about this to know what is going on. How do I get the value out for the key named listing?
Is this now just a string rather than an array? Do I need to convert it back to something else? JSON? I've tried using different JavaScript array methods on the array, and nothing seems to return what it should if the data was an array.
here is a way to get the elements out of your json string
as stated in the other answers, you should make it an obect again and get its keys and values.
function demo(){
var string='{"C8_235550":{"listing":"aut,C8_235550_220144650654"},"C8_231252":{"listing":"aut,C8_231252_220144650654"}}';
var ob = JSON.parse(string);
for(var propertyName in ob) {
Logger.log('first level key = '+propertyName);
Logger.log('fisrt level values = '+JSON.stringify(ob[propertyName]));
for(var subPropertyName in ob[propertyName]){
Logger.log('second level values = '+ob[propertyName][subPropertyName]);
}
}
}
What you have is an object, not an array. What you need to do is, use the
Object.keys()
method and obtain a list of keys which is the field names in that object. Then you could use a simple for loop to iterate over the keys and do whatever you need to do.
I am dynamically building an array of objects using a process that boils down to something like this:
//Objects Array
var objects = [];
//Object Structure
var object1 = {"id":"foobar_1", "metrics":90};
var object2 = {"id":"some other foobar", "metrics":50};
objects[0] = object1;
objects[1] = object2;
(Let it be said for the record, that if you can think of a better way to dynamically nest data such that I can access it with objects[i].id I am also all ears!)
There's ultimately going to be more logic at play than what's above, but it's just not written yet. Suffice it to say that the "object1" and "object2" parts will actually be in an iterator.
Inside that iterator, I want to check for the presence of an ID before adding another object to the array. If, for example, I already have an object with the ID "foobar_1", instead of pushing a new member to the array, I simply want to increment its "metrics" value.
If I wasn't dealing with an array of objects, I could use inArray to look for "foobar_1" (a jQuery utility). But that won't look into the object's values. The way I see it, I have two options:
Keep a separate simple array of just the IDs. So instead of only relying on the objects array, I simply check inArray (or plain JS equivalent) for a simple "objectIDs" array that is used only for this purpose.
Iterate through my existing data object and compare my "foobar_1" needle to each objects[i].id haystack
I feel that #1 is certainly more efficient, but I can't help wondering if I'm missing a function that would do the job for me. A #3, 4, or 5 option that I've missed! CPU consumption is somewhat important, but I'm also interested in functions that make the code less verbose whether they're more cycle-efficient or not.
I'd suggest switching to an object instead of an array:
var objects = {};
objects["foobar_1"] = {metrics: 90};
objects["some other foobar"] = {metrics: 50};
Then, to add a new object uniquely, you would do this:
function addObject(id, metricsNum) {
if (!(id in objects)) {
objects[id] = {metrics: metricsNum};
}
}
To iterate all the objects, you would do this:
for (var id in objects) {
// process objects[id]
}
This gives you very efficient lookup for whether a given id is already in your list or not. The only thing it doesn't give you that the array gave you before is a specific order of objects because the keys of an object don't have any specific order.
Hmm , i wonder why dont you use dictionary cause that is perfectlly fits your case. so your code will be as below:
//Objects Array
var objects = [];
//Object Structure
var object1 = {"metrics":90};
var object2 = {"metrics":50};
objects["foobar_1"] = object1;
objects["some other foobar"] = object2;
// An example to showing the object existence.
if (!objects["new id"]){
objects["new id"] = {"metrics": 100};
}
else {
objects["new id"].matrics++;
}
I have a javascript associative array like one below
var my_cars= new Array()
my_cars["cool"]="Mustang";
my_cars["family"]="Station Wagon";
my_cars["big"]="SUV";
I want to convert it using Stringify to json object. I want to know after conversion how the json object will look like.
Also when i have this object How I can convert it back to associative array again.
First of all, by making my_cars an array and stringifying it, you don't get what you expect.
var my_cars= new Array()
my_cars["cool"]="Mustang";
my_cars["family"]="Station Wagon";
my_cars["big"]="SUV";
alert(JSON.stringify(my_cars));
This alerts [].
What you want is to start with {}:
var my_cars= {};
my_cars["cool"]="Mustang";
my_cars["family"]="Station Wagon";
my_cars["big"]="SUV";
alert(JSON.stringify(my_cars));
This alerts
{"cool":"Mustang","family":"Station Wagon","big":"SUV"}
To get your object back from the string, use JSON.parse().
var s = JSON.stringify(my_cars);
var c = JSON.parse(s);
alert(c.cool);
This alerts "Mustang".
See http://jsfiddle.net/Y2De9/
No,But the user want to use array not json.
Normal JavaScript arrays are designed to hold data with numeric indexes. You can stuff named keys on to them (and this can be useful when you want to store metadata about an array which holds normal, ordered, numerically indexed data), but that isn't what they are designed for. The JSON array data type cannot have named keys on an array.
If you want named keys, use an Object, not an Array.
*source
var test = []; // Object
test[0] = 'test'; //this will be stringified
Now if you want key value pair inside the array
test[1] = {}; // Array
test[1]['b']='item';
var json = JSON.stringify(test);
output
"["test",{"b":"item"}]"
so you can use an index with array,so alternatively
var my_cars= [];
my_cars[0]={};
my_cars[0]["cool"]="Mustang";
my_cars[1]={};
my_cars[1]["family"]="Station Wagon";
my_cars[2]={};
my_cars[2]["big"]="SUV";
console.log(JSON.stringify(my_cars));
Output
"[{"cool":"Mustang"},{"family":"Station Wagon"},{"big":"SUV"}]"
Moving my comment into an answer so I can show you a code example.
These types of array are no-no's in javascript. You should ONLY use an object for non-numeric keys like this. Array indexes should be numbers. Javascript objects can use arbitrary values for keys (like in your example). Arrays happen to "appear" to work because Arrays themselves are objects, but you will not find normal Array methods will work on them. For example, look at this code example.
var my_cars= new Array()
my_cars["cool"]="Mustang";
my_cars["family"]="Station Wagon";
my_cars["big"]="SUV";
alert(my_cars.length); // alerts 0
You have only added properties to the underlying object, not actually added elements to the Array. You should use an Object for this, not an Array. Javascript does not actually have an Associative Array. It has an Object who's properties can often be used like one would use an Associate Array in other languages. But, it's an Object, not an Array.
"JavaScript does not support arrays with named indexes"
The most close state to an associative array is an array with entries converted to properties (as in your case), so I provide a solution for this exact case.
The fun thing is that Chrome's console makes it feel like an associative array: ["cool":"Mustang", "family":"Station Wagon", "big":"SUV"] (Check with F12)
NOTE: open browser's console before running the snippet
var my_cars= new Array()
my_cars["cool"]="Mustang";
my_cars["family"]="Station Wagon";
my_cars["big"]="SUV";
let toAssociative=(keys, values)=>
values.reduce((acc, cv)=>{
acc[acc.shift()]=cv
return acc;
}, keys)
let fromAssociative = (assArr)=>({...assArr})
let serialized = JSON.stringify(fromAssociative(my_cars))
let o = JSON.parse(serialized)
let restored = toAssociative(Object.keys(o) , Object.values(o))
//NOTE: Look at the browser's console before executing (not SO console)
console.log("orig:",my_cars)
//[cool: "Mustang", family: "Station Wagon", big: "SUV"]
console.log("serialized:",serialized)
//{"cool":"Mustang","family":"Station Wagon","big":"SUV"}
console.log("restored:",restored) //NOTE: look at the browser's console (F12)
//[cool: "Mustang", family: "Station Wagon", big: "SUV"]
If for some reason you cannot convert your array into object, for instance you are working on a big framework or legacy code that you dont want to touch and your job is only to add som feature which requires JSON API use, you should consider using JSON.stringify(json,function(k,v){}) version of the API.
In the function you can now decide what to do with value of key is of a specific type.
I am kind of new to the world of interface, and i found JSON is amazing, so simple and easy to use.
But using JS to handle it is pain !, there is no simple and direct way to push a value, check if it exists, search, .... nothing !
and i cannot simply add a one single value to the json array, i have this :
loadedRecords = {}
i want to do this :
loadedRecords.push('654654')
loadedRecords.push('11')
loadedRecords.push('3333')
Why this is so hard ???!!!
Because that's an object, not an array.
You want this:
var = loadedRecords = []
loadedRecords.push('1234');
Now to your points about JSON in JS:
there is no simple and direct way to push a value
JSON is a data exchange format, if you are changing the data, then you will be dealing with native JS objects and arrays. And native JS objects have all kinds of ways to push values and manipulate themeselves.
check if it exists
This is easy. if (data.someKey) { doStuff() } will check for existence of a key.
search
Again JSON decodes to arrays and objects, so you can walk the tree and find things like you could with any data structure.
nothing
Everything. JSON just translates into native data structures for whatever language you are using. At the end of the day you have objects (or hashes/disctionaries), and arrays which hold numbers strings and booleans. This simplicity is why JSON is awesome. The "features" you seek are not part of JSON. They are part of the language you are using to parse JSON.
Well .push is an array function.
You can add an array to ur object if you want:
loadedRecords = { recs: [] };
loadedRecords.recs.push('654654');
loadedRecords.recs.push('11');
loadedRecords.recs.push('3333');
Which will result in:
loadedRecords = { recs: ['654654', '11', '3333'] };
{} is not an array is an object literal, use loadedRecords = []; instead.
If you want to push to an array, you need to create an array, not an object. Try:
loadedRecords = [] //note... square brackets
loadedRecords.push('654654')
loadedRecords.push('11')
loadedRecords.push('3333')
You can only push things on to an array, not a JSON object. Arrays are enclosed in square brackets:
var test = ['i','am','an','array'];
What you want to do is add new items to the object using setters:
var test = { };
test.sample = 'asdf';
test.value = 1245;
Now if you use a tool like FireBug to inspect this object, you can see it looks like:
test {
sample = 'asdf,
value = 1245
}
Simple way to push variable in JS for JSON format
var city="Mangalore";
var username="somename"
var dataVar = {"user": 0,
"location": {
"state": "Karnataka",
"country": "India",
},
}
if (city) {
dataVar['location']['city'] = city;
}
if (username) {
dataVar['username'] = username;
}
Whats wrong with:
var loadedRecords = [ '654654', '11', '333' ];