I am new to JavaScript and wondering how can I compare an array with another array consists of JavaScript objects.
The array is a series of sorted time in the "YYYY-MM-DD" format.
The array of objects missed some price values of several days.
I want to find the missed value and assign it as "NULL".
For example, I have an array as:
array = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
and an array with objects as:
objArray = [{
date:"2014-10-09",
price:"100"
},
{
date:"2014-10-10",
price:"99"
},
{
date:"2014-10-12",
price:"102"
}];
I want to get the price array in this way:
priceResult = [100, 99, "NULL", 102];
What would be the most efficient way without using other libraries? I wanted to see if anyone had a more elegant solution. I deeply appreciate your help.
You can create a lookup set from the object array, then you can use that to translate the dates to prices.
This scales well, as it is an O(n+m) solution rather than the O(n*m) solution that you get if you use a loop in a loop to find the prices.
var array = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
var objArray = [{ date:"2014-10-09", model:"A", price:"100" },{ date:"2014-10-10", model:"A", price:"99" },{ date:"2014-10-12", model:"A", price:"102" }];
var lookup = {};
for (var i = 0; i < objArray.length; i++) {
lookup[objArray[i].date] = parseInt(objArray[i].price, 10);
}
var priceResult = [];
for (var i = 0; i < array.length; i++) {
if (lookup.hasOwnProperty(array[i])) {
priceResult.push(lookup[array[i]]);
} else {
priceResult.push('NULL');
}
}
// output result in StackOverflow snippet
document.write(JSON.stringify(priceResult));
Note: Instead of the string 'NULL' you might want to use the value null instead, as it is generally easier to handle.
lodash is the best library for this. But you did say "without using other libraries", so you will need to do it natively.
The easiest way to do it is nested for loops:
var i, j, d, res = [];
for (i=0; i<dateArray.length; i++) {
d = dateArray[i];
for (j=0; j<objArray.length; j++) {
if (objArray[j] && objArray[j].date && objArray[j].date === d) {
res.push(objArray[j].price);
j = objArray.length; // don't waste energy searching any more, since we found it
}
}
}
// res now contains all you wanted
If objArray is really big, and you don't want to search it multiple times, then you could turn it into an object indexed by date:
var i, obj = {}, d, res = [];
for (i=0; i<objArray.length; i++) {
if (objArray[i] && objArray[i].date) {
obj[objArray[i].date] = objArray[i];
}
}
for (i=0; i<dateArray.length; i++) {
d = dateArray[i];
res.push(obj[d] ? obj[d].price : null : null);
}
// res now contains all you wanted
Loop trough the object and search for the date in your array
// Add contains to array proto: http://css-tricks.com/snippets/javascript/javascript-array-contains/
var priceResult = [];
for(var i in objArray) {
if(dateArray.contains(objArray[i].date)) priceResult.push(objArray[i].date));
}
console.log('matches:', priceResult);
This function will give you map of all individual arrays in your object array
function getArrayMap(array) {
var map={}
for(var i=0;i<array.length;i++){
var o = array[i];
for(var k in o){
if(!map[k]){
map[k]=[];
}
map[k].push(o[k]);
}
}
return map;
}
you can use it like -
var map = getArrayMap(objArray);
console.log(map["date"]);//date array
console.log(map["price"]);//price array
console.log(map["model"]);//model array
If i am understanding your question correctly, for all the values in array, you want to check the objArr and find the price for each date, and if not found u want to inset null. If this is what you want, then following will help
var found= false;
var list=[];
for(var i=0; i< dateArray.length; i++)
{
for(var j=0; j< objArray.length; j++)
{
if(objArray[j].date == dateArray[i])
{
list.push(objArray[j].price);
found = true;
}
}
if(!found)
{
list.push("null");
}
found = false;
}
alert(list);
(I'm going to call your first array dates rather than array, to avoid confusion.)
There are basically two options:
Loop through your dates array and, for each entry, loop through the objArray looking for a match, and when found add to your priceResult array, or
Build a map from your objArray, then loop through yourdatesarray once, building thepriceResult` array.
Looping and Looping
You can loop through your dates array using forEach, and you can use Array#some to find out whether your objArray contains the date and add to priceResult if so (it's an ES5 feature, but you can polyfill it for really old browsers):
var priceResult = [];
dates.forEach(function(date) {
objArray.some(function(object) {
if (object.date == date) {
priceResult.push(object.price);
return true;
}
});
});
Array#some keeps looping until you return true, which is why we do that when we find the firs tmatch. That's why I say this is "looping and looping," even though we only write one loop, the other is within Array#some.
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [
{
date: "2014-10-09",
model: "A",
price: "100"
},
{
date: "2014-10-10",
model: "A",
price: "99"
},
{
date: "2014-10-12",
model: "A",
price: "102"
}
];
// Do it
var priceResult = [];
dates.forEach(function(date) {
objArray.some(function(object) {
if (object.date == date) {
priceResult.push(object.price);
return true;
}
});
});
snippet.log(priceResult.join(", "));
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>
Mapping and Looping
First, create a map of prices by date:
var prices = {};
objArray.forEach(function(object) {
prices[object.date] = object.price;
});
...then create your results:
var priceResult = [];
dates.forEach(function(date) {
if (prices.hasOwnProperty(date)) {
priceResult.push(prices[date]);
}
});
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [
{
date: "2014-10-09",
model: "A",
price: "100"
},
{
date: "2014-10-10",
model: "A",
price: "99"
},
{
date: "2014-10-12",
model: "A",
price: "102"
}
];
// Create the map
var prices = {};
objArray.forEach(function(object) {
prices[object.date] = object.price;
});
// Create your results:
var priceResult = [];
dates.forEach(function(date) {
if (prices.hasOwnProperty(date)) {
priceResult.push(prices[date]);
}
});
// Show them
snippet.log(priceResult.join(", "));
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>
var dates = ['2014-10-09','2014-10-10','2014-10-11','2014-10-12'];
var objArray = [{date:"2014-10-09", model:"A", price:"100" }, {date:"2014-10-10", model:"A", price:"99" }, {date:"2014-10-12", model:"A", price:"102" }];
var val;
var priceResult = [];
for (var a in dates) {
val = null;
for (var b in objArray) {
if (dates[a] == objArray[b].date) {
val = objArray[b].price;
}
}
priceResult.push(val);
}
var dates = ['2014-10-09', '2014-10-10', '2014-10-11', '2014-10-12'];
var objArray = [{
date: "2014-10-09",
model: "A",
price: "100"
}, {
date: "2014-10-10",
model: "A",
price: "99"
}, {
date: "2014-10-12",
model: "A",
price: "102"
}];
var val;
var priceResult = [];
for (var a in dates) {
val = null;
for (var b in objArray) {
if (dates[a] == objArray[b].date) {
val = objArray[b].price;
}
}
priceResult.push(val);
}
// output result in StackOverflow snippet
document.write(JSON.stringify(priceResult));
Try this:
var temp[]
temp= jQuery.grep(objArray , function (n, i)
{
for(j=0;j<dateArray.lenght+j++ )
if( n.date === dateArray[j])
return n.price;
);
dateArray = ["2014-10-09", "2014-10-10", "2014-10-11", "2014-10-12"];
function ObjectExample(date1,model,price)
{
this.date1 = date1;
this.model = model;
this.price = price;
}
var objArray = [new ObjectExample("2014-10-09","A","100"), new ObjectExample("2014-10-10","A","99"), new ObjectExample("2014-10-12","A","102")];
var i = 0;
var priceDate = new Array();
var count = 0;
while(i < dateArray.length)
{
var j = 0;
while(j < objArray.length)
{
if(dateArray[i] == objArray[j].date1)
{
priceDate[count] = objArray[j].price;
break;
}
else priceDate[count] = "NULL";
j = j + 1;
}
i = i + 1;
count++;
}
document.write(priceDate);
I am facing issues while constructing an object using javascript. I want this:
{
"p_id": "2",
"p_name": "weblogic",
"ip_list": [
{
"ip_id": 2690
},
{
"ip_id": 2692
},
{
"ip_id": 2693
}
]
}
Below is the javascript code that I am using to get the data into the object:
var ipArray = [];
secTagJSON.p_name = "weblogic";
secTagJSON.p_id = "2";
for (var index=0; index < selectedArray.length; index++){
secTagJSON.ip_list.push("ip_id": selectedArray[index]);
}
I am able to construct the properties for p_id and p_name but struggling to create the the ip_list. Please let me know how to get this constructed using javascript.
Code for posting to the server:
var ipArray = [];
secTagJSON.p_name = "weblogic";
secTagJSON.p_id = 2;
for (var index=0; index < selectedArray.length; index++){
secTagJSON.ip_list.push({"ip_id": selectedArray[index]});
}
console.log (secTagJSON);
console.log (JSON.stringify(secTagJSON));
$http.post("http://server:port/api/v1/tags").
success(function(data) {
console.log (data)
});
Simply do this:
var obj = { ip_list: [] };
obj.p_name = "weblogic";
obj.p_id = "2";
for (var i = 0, j = selectedArray.length; i < j; i++)
obj.ip_list.push({ ip_id: selectedArray[i] });
Note that your ip_list is actually an array of objects. So, when you iterate over it, remember that each var item = json.ip_list[i] will return an object, that you can access its properties using: item['ip_id'].
Note that obj is an Javascript object, it is not an JSON. If you want the JSON, you can use JSON.stringify(obj). This will return your JSON (string).
Hope I've helped.
Try:
secTagJSON.p_name = "weblogic";
secTagJSON.p_id = "2";
secTagJSON.ip_list = [];
for (var index=0; index < selectedArray.length; index++){
secTagJSON.ip_list.push({"ip_id": selectedArray[index]});
}
you forgot your {} around "ip_id": etc...
You also need to declare that ip_list is an array.
Your ip_list is an array of objects. I would guess that your script was not running as it was.
Posting to your server you should use:
$http.post('server:port/api/v1/tags', secTagJSON).sucess(...
Firstly, this is my json value i am getting from a php source:
[{"oid":"2","cid":"107"},{"oid":"4","cid":"98"},{"oid":"4","cid":"99"}]
After that, I want to get and oid value along with the corresponding cid value for example, oid=2 and cid=107 at one go, oid=4 and cid=98 at another and so on. I am trying to use jquery, ajax for this.
I have tried many answers for this, like: Javascript: Getting all existing keys in a JSON array and loop and get key/value pair for JSON array using jQuery but they don't solve my problem.
I tried this:
for (var i = 0; i < L; i++) {
var obj = res[i];
for (var j in obj) {
alert(j);
}
but all this did was to return the key name, which again did not work on being used.
So, you have an array of key/value pairs. Loop the array, at each index, log each pair:
var obj = [{"oid":"2","cid":"107"},{"oid":"4","cid":"98"},{"oid":"4","cid":"99"}];
for (var i = 0; i < obj.length; i++) {
console.log("PAIR " + i + ": " + obj[i].oid);
console.log("PAIR " + i + ": " + obj[i].cid);
}
Demo: http://jsfiddle.net/sTSX2/
This is an array that you have //lets call it a:
[{"oid":"2","cid":"107"},{"oid":"4","cid":"98"},{"oid":"4","cid":"99"}]
To get first element :
a[0] // this will give you first object i.e {"oid":"2","cid":"107"}
a[0]["oid"] // this will give you the value of the first object with the key "oid" i.e 2
and so on ...
Hope that helps.
`
Basically what you need is grouping of objects in the array with a property. Here I am giving two functions using which you can do this
// To map a property with other property in each object.
function mapProperties(array, property1, property2) {
var mapping = {};
for (var i = 0; i < data.length; i++) {
var item = data[i];
mapping[item[property1]] = mapping[item[property1]] || [];
mapping[item[property1]].push(item[property2]);
}
return mapping;
}
// To index the items based on one property.
function indexWithProperty(array, property) {
var indexing = {};
for (var i = 0; i < data.length; i++) {
var item = data[i];
indexing[item[property]] = indexing[item[property]] || [];
indexing[item[property]].push(item);
}
return indexing;
}
var data = [{
"oid": "2",
"cid": "107"
}, {
"oid": "4",
"cid": "98"
}, {
"oid": "4",
"cid": "99"
}];
var oidCidMapping = mapProperties(data, "oid", "cid");
console.log(oidCidMapping["2"]); // array of cids with oid "2"
var indexedByProperty = indexWithProperty(data, "oid");
console.log(indexedByProperty["4"]); // array of objects with cid "4"
May not be the exact solution you need, but I hope I am giving you the direction in which you have to proceed.
If you are willing to use other library you can achieve the same with underscorejs
I have this JS object:
{
"data": {
"nid": [{
"cid": "32",
"uid": "780",
"comment": "text"
}]
},
"request_status": "found"
}
how can I loop through these items to get comment value ("comment":"text")?
You don't really need to loop to get it. Just do...
var obj = {"data":{"nid":[{"cid":"32","uid":"780","comment":"text"}]},"request_status":"found"};
var text = obj.data.nid[0].comment;
Or if there are several, you can use forEach...
obj.data.nid.forEach(function(val,i) {
alert( val.comment );
});
Or a traditional for loop...
for( var i = 0; i < obj.data.nid.length; i++ ) {
alert( obj.data.nid[i].comment );
}
Or if you want to build an Array, use map...
var arr = obj.data.nid.map(function(val,i) {
return val.comment;
});
Or again a traditional for loop...
var arr = []
for( var i = 0; i < obj.data.nid.length; i++ ) {
arr.push( obj.data.nid[i].comment );
}
Given:
var obj = {
"data": {
"nid": [{
"cid": "32",
"uid": "780",
"comment": "text"
}]
},
"request_status": "found"
};
The direct way to retrieve the comment is:
obj["data"]["nid"][0]["comment"]
// or
obj.data.nid[0].comment
As far as "looping" through the items to get the value, I'm not sure how a loop makes sense. Are you saying you might not know the structure of the object but you know it will have a "comment" field in there somewhere?
The "nid" array only has one item in it - if this was just a sample but really you'll have an array with more values you can loop through that array:
var nid = obj["data"]["nid"], // get a direct reference to the array to save
i; // repeating obj.data.nid everywhere
for (i=0; i < nid.length; i++) {
// do something with the comment in the current item
console.log(nid[i]["comment"]);
}
If you're just referring to that specific object (or if every object you are working with follows that same pattern), then you can just access the value directly:
var theObj = {"data":{"nid":[{"cid":"32","uid":"780","comment":"text"}]},"request_status":"found"};
alert(theObj.data.nid[0].comment);
If you want to do something iterative, then perhaps try this:
var theObj = {"data":{"nid":[{"cid":"32","uid":"780","comment":"text"}]},"request_status":"found"};
for (var index = 0; index < theObj.data.nid.length; index++) {
var item = theObj.data.nid[index];
if (item.comment) {
alert(item.comment);
}
}
Or if you really want to do the entire thing iteratively:
window.searchObj = function(theObj) {
if (theObj.comment) {
alert(theObj.comment);
}
if (theObj instanceof Array) {
searchArray (theObj);
}
else if (theObj instanceof Object) {
for (var key in theObj) {
searchObj(theObj[key]);
}
}
};
window.searchArray = function(theArray) {
for (var index = 0; index < theArray.length; index++) {
var item = theArray[index];
searchObj(item);
}
};
var theObj = {"data":{"nid":[{"cid":"32","uid":"780","comment":"text"}]},"request_status":"found"};
searchObj(theObj);
Im having some issues creating an array of objects in javascript
Please see my code below and tell me where im going wrong..
I simply want to loop through and access the values
<!-- Read XML Script -->
<script type="text/javascript">
// Object array
var myArray = [];
$(document).ready(function () {
$.ajax({
type: "GET",
url: "HighScore.xml",
dataType: "xml",
success: function (xml) {
$(xml).find('challenger').each(function () {
var name = $(this).find('Name').text();
var watts = $(this).find('Watts').text();
var Mins = $(this).find('Mins').text();
// objects in the array
challenger = new Object();
challenger.name = name;
challenger.watts = watts;
challenger.Mins = Mins;
myArray.push(challenger);
});
// look into the array
for (obj in myArray) {
// do i need to cast ?? how can i view the object ??
alert(obj + " - ");
}
},
error: function () {
alert("error");
}
});
});
</script>
The for .. in .. works different in javascript than in some other languages. Instead of the object, you will get the key. In your array therefore you'll get the index.
For iterating over arrays, just use an index-based array to avoid hassle:
for (var ix = 0; ix < myArray.length; ix++) {
var obj = myArray[ix];
alert(obj.name);
}
If you really want to use the for .. in .. syntax, use this:
var a = ['jan', 'klaas'];
for(var key in a) {
if (a.hasOwnProperty(key)) {
console.log(a[key].name);
}
}
- for (obj in myArray) {
- // do i need to cast ?? how can i view the object ??
- alert(obj + " - ");
- }
+ for (var i = 0; i < myArray.length; i++) {
+ var obj = myArray[i];
+ // do i need to cast ?? how can i view the object ??
+ alert(JSON.stringify(obj, null, ' '));
+ }