I have an array of objects like so
myobj= [{"item1" : info in here},{"item2" : info in here}, {"item3" : info in here}]
I'm trying to modify one, but I only know its key. I need to pinpoint the item1 object so I can change its value (the values are random and I don't know them, so I can't rely upon them).
If I could just get the index of the item it would be pretty easy: myobj[index].value = "newvalue".
Maybe using the index isn't the best way, so if it isn't, I'm open to other ideas.
I was thinking I could try something like
myobj.objectVar
Where objectVar is the key I'm being passed (item1, for example), however this does not work, possibly because it's a variable? Is it possible to use a variable like this maybe?
If it helps, I'm using underscore.js as well.
Your guess at a solution doesn't work because you're not accessing the individual objects, you're accessing an array of objects, each of which has a single property.
To use the data in the format you've got now, you need to iterate over the outer array until you find the object that contains the key you're after, and then modify its value.
myobj= [{"item1" : info in here},{"item2" : info in here}, {"item3" : info in here}]
function setByKey(key, value) {
myObj.forEach(function (obj) {
// only works if your object's values are truthy
if (obj[key]) {
obj[key] = value;
}
});
}
setByKey('item1', 'new value');
Of course, the far better solution is to stop using an array of single-property objects, and just use one object with multiple properties:
myobj= {"item1" : info in here, "item2" : info in here, "item3" : info in here};
Now, you can simply use myObject.item1 = "some new value" and it will work fine.
You can write a function like,
function getElementsHavingKey(key) {
var objectsHavingGivenKey = [];
//loop through all the objects in the array 'myobj'
myobj.forEach(function(individualObject) {
//you can use 'hasOwnProperty' method to find whether the provided key
// is present in the object or not
if(individualObject.hasOwnProperty(key)) {
// if the key is present, store the object having the key
// into the array (many objects may have same key in it)
objectsHavingGivenKey.push(individualObject);
}
});
// return the array containing the objects having the keys
return objectsHavingGivenKey;
}
If you only want to get the index of elements having the given key
You can do something like this,
function getIndexesOfElementsHavingKey(key) {
var objectsHavingGivenKey = [];
//loop through all the objects in the array 'myobj'
myobj.forEach(function(individualObject, index) {
//you can use 'hasOwnProperty' method to find whether the provided key
// is present in the object or not
if(individualObject.hasOwnProperty(key)) {
//push index of element which has the key
objectsHavingGivenKey.push(index);
}
});
// returns the array of element indexes which has the key
return objectsHavingGivenKey;
}
Try this code:
function changeObj( obj, key, newval )
{
for( var i=0, l=obj.length; i<j; i++)
{
if( key in obj[i] )
{
obj[i] = newval;
return;
}
}
}
var myObjArray= [{"item1" : "info in here"},{"item2" : "info in here"}, {"item3" : "info in here"}]
To find and add new value to the object inside an array:
myObjArray.forEach(function(obj) {
for(var key in obj) {
// in case you're matching key & value
if(key === "item1") {
obj[key] = "update value";
// you can even set new property as well
obj.newkey = "New value";
}
}
});
You can access objects the same using their index, even the object inside the original object.
Is this kind of what your looking for:
var otherObj = [{"oitem":"oValue"}];
var myobj= [{"item1" : otherObj},{"item2" : "2"}, {"item3" : "tesT"}];
myobj[0].item1[0].oitem = "newvalue";
alert(myobj[0].item1[0].oitem);
Related
I'm making a dictionary of words, so there are 1,000,000+ words.
The problem comes when I need to store the word constructor. I know this is a reserved word in javascript, but I need to add it to the dictionary.
var dictionary = {}
console.log(dictionary ['word_1'])
//undefined, this is good
console.log(dictionary ['word_2'])
//undefined, this is good
console.log(dictionary ['constructor'])
//[Function: Object]
// this cause initialization code to break
How can I fix this? I could muck with the it like key=key+"_" but that seems bad. Is there anything else I can do?
Instead of using a JS object, you could use the built-in Map type which uses strings/symbols as keys and does not conflict with any existing properties.
Replace
var dictionary = {} with var dictionary = new Map()
Override the constructor key as undefined
According to the MDN Object.prototype page, the only thing that isn't hidden by the __fieldname__ schema is the "constructor field". Thus, you could just initialize your objects via { 'constructor': undefined }.
However, you would have to make sure that in your for .. in statements would filter out all keys with undefined as their value, as it would pick up constructor as a "valid" key (even though it wouldn't before you specifically set it to undefined). I.E.
for(var key in obj) if(obj[key] !== undefined) { /* do things */ }
Check for types when getting/setting
Otherwise, you could just check the type when you 'fetch' or 'store' it. I.E.
function get(obj, key) {
if(typeof obj[key] !== 'function') // optionally, `&& typeof obj[key] !== 'object')`
return obj[key];
else
return undefined;
}
I think you should store all words and translation of them in an array. When you need to translate a word, you can use find method of Array.
For example:
var dict = [
{ word: "abc", translated: "xyz" },
...
];
Then:
var searching_word = "abc";
var translation = dict.find(function (item) {
return item.word == searching_word;
});
console.log(translation.translated);
// --> xyz
To achieve expected result , use below option of using index to get value of any key value
var dictionary = {};
var dictionary1 = {
constructor: "test"
};
//simple function to get key value using index
function getVal(obj, val) {
var keys = Object.keys(obj);
var index = keys.indexOf(val);//get index of key, in our case -contructor
return obj[keys[index]]; // return value using indec of that key
}
console.log(getVal(dictionary, "constructor"));//undefined as expected
console.log(getVal(dictionary1, "constructor"));//test
console.log(dictionary["word_1"]);
//undefined, this is good
console.log(dictionary["word_2"]);
//undefined, this is good
codepen - https://codepen.io/nagasai/pen/LOEGxM
For testing , I gave one object with key-constructor and other object without constructor.
Basically I am getting the index of key first and getting value using index
i am having trouble to get object property name from this data that i retrieve from some API server :
var arrData = [{"data":
{"plmn":"Voda","id":"B193","time":1499257121817,"cell":{"rsrp":
[-132.5,-108.88],"rsrq":[-18.69,-6.56],"earfcn":1550,"pci":454,"celltiming":
[252],"sinr":-12.8,10.7]},"mac":"9C65F9"},"time":1499282331405,
},{"data":
{"plmn":"Voda","rssi":-106,"id":"4179","time":315939662698,"cells":
[{"sc":453,"ecno":-19.53,"r99":"intraMon","rscp":-125.53,"ch":10837},
{"sc":452,"ecno":-13.97,"r99":"active","rscp":-119.97,"ch":10837},
{"sc":452,"ecno":-19.53,"r99":"active","rscp":-125.53,"ch":10812},
{"sc":453,"ecno":-19.37,"r99":"intra","rscp":-125.37,"ch":10812}],"mac":
"9C65F9211012"},"time":1499282452590,"deviceID":"9C65F9211012"}]
i already try with this code :
var collectField = [];
for (var prop in arrData) {
if (arrData.hasOwnProperty(prop)) {
collectField.push(prop);
}
}
// and still wrong Outputs: [0,1,2,3.....]
console.log(collectField);
the output result that i expected :
[plmn,id,time,cell,,ecno,cells,rscp..and all of that object field]
hope someone can help this problem.
Thanks in advance
for-in construct doesn't retrieve the object from array but it's index. So you're trying to access hasOwnProperty on the number. First you need to access array member and then property eg. like this:
for (var index in arrData) {
var obj = arrData[index];
if (obj.hasOwnProperty(prop)) {
collectField.push(obj[prop]);
}
}
I want to create data structure like that.
Var ans =[{"b":[1,2]},{"g":[100,2]}]
I want to create a new object within list if key not exists in list ans.
Else if key exists in one object of ans list then I want to add new values into the object of ans list
For Example:
Example 1) new data c:{2000}
then
Var ans =[{"b":[1,2]},{"g":[100,2]},{c:[2000]}]
Example 2) new data g:{50}
then
Var ans =[{"b":[1,2]},{"g":[100,2,500]},{c:[2000]}]
I am a beginner in node js, understand array, object concept, but not getting exact logic!
Thanks!
You can try following:
Logic
Filter array based on key
Check if object with mentioned key exists or not.
If yes, push value to this array.
If not, create a dummy object and push this object to original array.
Correction, when you do .push({key: value}), key will be considered as string.
Alternates
If you are using ES6, .push({ [key] : value })
Create a dummy object var o = {}. Set key and value to it o[key] = value and push this object.
Optimisations
Instead of setting value like obj[key] = value, since we will be operating on arrays, try obj[key] = [].concat(value). This will enable you to pass value as number or array of values.
Instead of checking the existence of value in .filter, try Array.isArray to check if value exists and is of type array.
Custom function
function checkAndPush(array, key, value) {
var filteredList = array.filter(function(o) {
return Array.isArray(o[key]);
});
filteredList.length > 0 ? filteredList[0][key].push(value) : array.push({
[key]: [].concat(value)
});
return array;
}
var ans =[{"b":[1,2]},{"g":[100,2]}]
console.log(checkAndPush(ans, "c", [2,3]))
console.log(checkAndPush(ans, "c", 4));
Prototype function
Array.prototype.checkAndPush = function(key, value) {
var filteredList = this.filter(function(o) {
return Array.isArray(o[key]);
});
var dummy = {}
dummy[key] = [].concat(value)
filteredList.length > 0 ? filteredList[0][key].push(value) : this.push(dummy);
// or ES6: this.push({ [key]: [].concat(value) })
return this;
}
var ans =[{"b":[1,2]},{"g":[100,2]}]
console.log(ans.checkAndPush("c", [2,3]))
console.log(ans.checkAndPush("c", 4));
If you are dealing with objects as your values
ans[key] = ans[key] || []
ans[key].push(value)
Note, this works because your values will be an array. If they could be primatives then you would use hasOwnProperty to check.
if (ans.hasOwnProperty(key)) {
// Add this to your key somehow
} else {
// initialize the key with your value
}
Node.js is nothing but a library built on javascript. You can do anything using javascript type of progmming. However push and pop method should be able to help you to deal with nodejs array.
ans[key].push(value)
So I have an object. I want to iterate over it and return same object but with additional attributes. I have done the following but it returns old data.
_.each(data, function(item) {
_.extend(item, {name: item.first});
});
Ok i have even tried, still no luck
_.each(data, function (item){
item.name = item.first;
return item;
});
You can better use Array.map for this
var newData = data.map(function(i){
i['name'] = i.first;
return i;
})
var data = {
a : { first : 'albert'},
b : { first : 'bob' },
c : { first : 'charle'}
};
for ( var item in data ) {
data[item].name = data[item].first;
}
If you want to change an object you should not "return" it, because is nonsense, javascript doesn't copy object anyway, return will give a link to the same data object, and if you change this object will change data too, if you really nead a diferent object, you will need do a deep copy of your object.
Exemple:
a = {name:'albert'};
b = a;
b.name = 'bob';
console.log(a);
will show { name: 'bob' }
That is beacause extend copies the second object's properties in the first: http://underscorejs.org/#extend
Im not sure what you want, but won't this fix it?
_.each(data, function(item) {
//set item.first property on item.name
item.name = item.first;
});
//var data is still the same array with same objects, but all the objects inside are updated.
based on your comment
here you go, what you want:
var yourNewArray = data.map(function(item){
//clone item so you dont have reference to object in dat array
var newItem = _.clone(item);
//set property on another property
newItem.name = newItem.first;
return newItem;
}
another way
Another way if you only want that specific proprety as object array:
var yourNewArray = data.map(function(item){
return { name : item.first}; //return object with property name, with value from original object.first property
}
Remember: an array contains an list of object References. So you cant simply change the objects, you need to clone them so you don't change the original array.
I have a js object that looks like this:
var object = {
"divisions": {
"ocd-division/country:us": {
"name": "United States",
}
}
};
I want to access the property listed under the nested object "ocd-division/country:us" (aka "name"), but the problem I'm having is that "ocd-division/country" is a variable object. Like it might be ":can" for Canada or something.
My question is, can I still access the name property under that object even though it's variable? I wrote the code I came up with below, but it calls the object literally, so it can't account for a change in the object's name.
var country = document.getElementById("p");
p.innerHTML = object.divisions["ocd-division/country:us"].name;
I'm new to JavaScript so I'm sorry if this is a dumb question.
When you don't know the properties of an object, you can use
for...in loop
It iterates enumerable own and enumerable inherited properties.
Object.keys
It returns an array which contains enumerable own properties.
Object.getOwnPropertyNames
It returns an array which contains own properties.
// Adding properties: "ownEnumerable", "ownNonEnumerable",
// "inheritedEnumerable" and "inheritedNonEnumerable"
var obj = Object.defineProperties({}, {
ownEnumerable: {enumerable: true},
ownNonEnumerable: {},
});
Object.defineProperties(Object.prototype, {
inheritedEnumerable: {enumerable: true},
inheritedNonEnumerable: {},
});
// Display results
function log(id, arr) {
document.getElementById(id).textContent = '[' + arr.join(', ') + ']';
}
log('forin', function(forInProps){
for (var prop in obj) forInProps.push(prop);
return forInProps;
}([]));
log('keys', Object.keys(obj));
log('names', Object.getOwnPropertyNames(obj));
<dl>
<dt><code>for...in</code></dt><dd id="forin"></dd>
<dt><code>Object.keys</code></dt><dd id="keys"></dd>
<dt><code>Object.getOwnPropertyNames</code></dt><dd id="names"></dd>
</dl>
object.divisions[Object.keys(object.divisions)[0]].name
Sure...
for (var division in object.divisions) {
var name = object.divisions[division].name;
// Do what you want with name here
}
If the object has prototype methods you will want to use Object.prototype.hasOwnProperty() to ensure they don't get iterated like so:
for (var division in object.divisions) {
if (!object.divisions.hasOwnProperty(division)) continue;
var name = object.divisions[division].name;
// Do what you want with name here
}
Or use Object.keys() if you don't care about IE8 support and iterate over those.
Object.keys(object.divisions).forEach(function(division) {
var name = object.divisions[division].name;
// Do what you want with name here
});
EDIT: Upon re-reading your question it occurs to me that you may already know the key name but want to access the object with a variable key name, which is also absolutely fine:
var division = 'ocd-division/country:us';
object.divisions[division].name;
When using [] bracket notation to access an object you can insert any code that evaluates to a string, you could even call a function in there that returns a string.
See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Property_Accessors
You can iterate through object using for loop.
var obj = {
"divisions":{
"ocd-division/country:us":{
"name" : "United States"
}
}
}
Here is the for loop
for(var a in obj){ //loop first the object
for(var b in obj[a]){ // then second object (divisions)
for(var c in obj[a][b]){ //then third object (ocd-division/country:us)
if(c == 'name'){ //c is the key of the object which is name
console.log(obj[a][b][c]); //print in console the value of name which is United States.
obj[a][b][c] = "Canada"; //replace the value of name.
var objName = obj[a][b][c]; //or pass it on variable.
}
}
}
}
console.log(obj); //name: Canada
console.log(objName); //name: United States
You can also use this reference:
https://developer.mozilla.org/enUS/docs/Web/JavaScript/Reference/Statements/for
http://stackoverflow.com/questions/8312459/iterate-through-object-properties