I have an object of values and I am trying to populate two arrays with the keys and values from the object.
My Object:
obj = {19455746: 7476, 22489710: 473}
Loop attempting to append data:
var sensorNameArray = [];
var sensorDataArray = [];
for(var i in obj) {
sensorNameArray.push[i];
sensorDataArray.push[obj[i]];
}
At the moment the two arrays are printing out as empty. My expected outout would be something like:
sensorNameArray = [19455746, 22489710];
sensorDataArray = [7476, 473];
push is a function, not an array, it uses parenthesis not brackets :
for(var i in obj) {
sensorNameArray.push(i);
sensorDataArray.push(obj[i]);
}
The syntax push[] doesn't invoke the function, it tries to access a property of the function object. It doesn't throw an error because in Javascript, functions ARE objects and this syntax is technically valid.
So, just fix the syntax to push() in order to actually invoke the function.
You are using square braces []
but array.push() is a function so use circle braces instead
Try the following code
obj = {19455746: 7476, 22489710: 473};
var sensorNameArray = [];
var sensorDataArray = [];
for(var i in obj) {
sensorNameArray.push(i);
sensorDataArray.push(obj[i]);
}
This is working and tested.
A different syntax (more elegant IMO) :
var sensorNameArray = Object.keys(obj)
var sensorDataArray = Object.values(obj)
or :
var sensorDataArray = sensorNameArray.map( key => obj[key] )
Best way to deal with JSON is use lodash or underscore.
_.key() and _.value are functions for your requirement.
Eg.:
obj = {19455746: 7476, 22489710: 473};
sensorNameArray = _.keys(obj);
sensorDataArray = _.values(obj);
If you want to proceed in your way, then you can use parenthesis as push inbuilt function of Javascript for inserting element into array.
Correct is:
for(var i in obj) {
sensorNameArray.push(i);
sensorDataArray.push(obj[i]);
}
Related
This question already has answers here:
Copy array by value
(39 answers)
Closed 8 years ago.
I have an array example fruit . I'd like to copy it as array fruits2, without keeping reference.
As in the following example reference is kept so fruits is modified.
var fruit = function (name){
this.name = name;
}
var fruits = [];
fruits.push(new fruit('apple'));
fruits.push(new fruit('banana'));
fruits.push(new fruit('orange'));
var fruits2 = fruits;
fruits2.length = 0;
console.log(fruits);
http://jsfiddle.net/vkdqur82/
Using JSON.stringify and JSON.parse does the trick but the objects in fruits2 are not any longer of type fruit but are of general type object
var temp = JSON.stringify(fruits);
var fruits2 = JSON.parse(temp);
I would like to know an alternative approach which would keep inner object of fruit.
Use slice: var fruits2 = fruits.slice(); should do it.
Your jsFiddle, modified
See also: MDN
**Edit. I was a bit lazy, let's correct my answer to make up for that.
For an Array of just values slice is perfect. For an Array of objects or arrays or a mix of values/objects/arrays, the Array and Object elements of the Array to clone need cloning too. Otherwise they will be references to the original arrays or objects (so: not copies) and a change of one [of these references of arrays or objects] will be reflected in all 'clones' containing a reference to it.
To clone an Array of Arrays/Objects/mixed values Array.map is your friend. There are several methods to think of:
creating a new instance with old data
var fruits1 = fruits.map(function(v) {return new Fruit(v.name);});
using JSON
var fruits2 = fruits.map(function(v) {return JSON.parse(JSON.stringify(v));});
create and use some cloning method
var fruits3 = fruits.map(function(v) {return cloneObj(v);});
In case 3, a method for cloning could look like:
function cloneObj(obj) {
function clone(o, curr) {
for (var l in o){
if (o[l] instanceof Object) {
curr[l] = cloneObj(o[l]);
} else {
curr[l] = o[l];
}
}
return curr;
}
return obj instanceof Array
? obj.slice().map( function (v) { return cloneObj(v); } )
: obj instanceof Object
? clone(obj, {})
: obj;
}
Using this cloneObj method, Array.map is obsolete.
You can also use var fruitsx = cloneObj(fruits);
The jsFiddle from the link above is modified to demonstrate these methods.
For Array.map, see again MDN
slice can do the trick.
You can also use .map but .slice is normally faster.
var copy = fruits.map(function(item) {return item});
Hope it helps
You can declare a new array and use concat method, so that you concat all values from your array to the new array. Something like this:
var x = ["a","b"];
var a = [];
a = a.concat(x);
console.log(a);
I edited my poor answer.
Best regards.
Is there a way for this line to always work and not throw TypeError: Cannot read property 'Whatever' of undefined
var MyArray = [];
MyArray[StringVariableName][StringVariableName2].push("whatever");
Try this:
var MyArray = [];
MyArray[StringVariableName] = MyArray[StringVariableName] || [];
MyArray[StringVariableName][StringVariableName2] = MyArray[StringVariableName][StringVariableName2] || [];
MyArray[StringVariableName][StringVariableName2].push("whatever");
You could even, through the power of expressions, do this with a one-liner.
(MyArray[StringVariableName][StringVariableName2] || (MyArray[StringVariableName][StringVariableName2] = [])).push("whatever");
You could use the literal syntax to set things up like you'd have them:
var myObj = {
StringVariableName: {
StringVariableName2: []
}
};
myObj.StringVariableName.StringVariableName2.push("whatever");
I think instead of using array in the first place, use object if your keys are not integers.
In Javascript Arrays are also object So it is not wrong to do this
var a = [];
a['key'] = 'something';
console.log(a); //Gives []
I think it is conceptually wrong So instead of using Array to hold such pair of data you should use objects. See this:
var myObject = myObject || {};
myObject[str1] = myObject[str1] || {};
myObject[str1][str2] = myObject[str][str2] || [];
// Now myObject[str1][str2] is an array. Do your original operation
myObject[str1][str2].push("whatever");
To check without getting an error:
this snippet allows you to check if a chained object exists.
var x;
try{x=MyArray[name1][name2][name3][name4]}catch(e){}
!x||(x.push('whatever'));
from
https://stackoverflow.com/a/21353032/2450730
Shorthand creation of object chains in Javascript
this function allows you to create chained objects with a simple string.
function def(a,b,c,d){
c=b.split('.');
d=c.shift();//add *1 for arrays
a[d]||(a[d]={});//[] for arrays
!(c.length>0)||def(a[d],c.join('.'));
}
usage
var MyArray={};//[]
def(MyArray,'name1.name2.name3.name4');//name1+'.'+name2....
from
https://stackoverflow.com/a/21384869/2450730
both work also for arrays with a simple change.replace {} with []
if you have any questions just ask.
This should be pretty easy but I'm a little confused here. I want to fill this object:
var obj = { 2:some1, 14:some2, three:some3, XX:some4, five:some5 };
but in the start I have this:
var obj = {};
I´m making a for but I don't know how to add, I was using push(), but is not working. Any help?
You can't .push() into a javascript OBJECT, since it uses custom keys instead of index. The way of doing this is pretty much like this:
var obj = {};
for (var k = 0; k<10; k++) {
obj['customkey'+k] = 'some'+k;
}
This would return:
obj {
customkey0 : 'some0',
customkey1 : 'some1',
customkey2 : 'some2',
...
}
Keep in mind, an array: ['some1','some2'] is basicly like and object:
{
0 : 'some1',
1 : 'some2'
}
Where an object replaces the "index" (0,1,etc) by a STRING key.
Hope this helps.
push() is for use in arrays, but you're creating a object.
You can add properties to an object in a few different ways:
obj.one = some1;
or
obj['one'] = some1;
I would write a simple function like this:
function pushVal(obj, value) {
var index = Object.size(obj);
//index is modified to be a string.
obj[index] = value;
}
Then in your code, when you want to add values to an object you can simply call:
for(var i=0; i<someArray.length; i++) {
pushVal(obj, someArray[i]);
}
For info on the size function I used, see here. Note, it is possible to use the index from the for loop, however, if you wanted to add multiple arrays to this one object, my method prevents conflicting indices.
EDIT
Seeing that you changed your keys in your questions example, in order to create the object, you can use the following:
function pushVal(obj, value, key) {
//index is modified to be a string.
obj[key] = value;
}
or
obj[key] = value;
I'm not sure how you determine your key value, so without that information, I can't write a solution to recreate the object, (as is, they appear random).
I have 3 arrays like:
var arr1 = [];
var arr2 = [];
var arr3 = [];
//When I want to add something into array then I use
arr1.push("text");
arr2.push("text");
but is it possible to make something like the following example?
//example:
var arr = [];
arr['group1'].push("text1");
arr['group2'].push("text2");
arr['group2'].push("textn");
//and then iterate like:
for(item in arr['group1'])
console.log(item);
is it even possible to do something like that? I have tried but does not work.
There's a fundamental misunderstanding though, arr is an array but you're using it as an associative array, which in JavaScript is better represented with an object {}. for...in is for objects, NOT arrays, the MDN has a warning note about it:
for..in should not be used to iterate over an Array where index order
is important...
I would advice even if index is trivial to use a regular for loop or a forEach.
Consider using the following, more appropiate approach.
var obj = {
group1: ['text1'],
group2: ['text2'],
group3: ['text3']
};
// pushing more strings
obj.group1.push('foo');
obj['group2'].push('baz');
You're treating arr['group1'] as an array (by using .push()), but you haven't declared it as an array.
var arr = [];
arr['group1'] = [];
arr['group2'] = [];
arr['group3'] = [];
arr['group1'].push("text1");
arr['group2'].push("text2");
arr['group2'].push("textn");
It seems you're actually looking for Javascript Objects instead of arrays.
Also, you need to create these objects first.
var obj = {group1:[],group2:[],group3:[]};
/* or
var obj = {};
obj.group1 = [];
*/
obj['group1'].push("text1");
// or obj.group1.push("text1");
The for...in structure sets your for variable to the key, not the value. Assuming arr['group1'] is an array, this will work fine:
//example:
var arr = [];
arr['group1'].push("text1");
arr['group2'].push("text2");
arr['group2'].push("textn");
//and then iterate like:
for(item in arr['group1'])
console.log(arr['group1'][item]);
I'm trying to add a key value pair to an existing javascript associative array. The key needs to be a variable. This is for JSON encoding. I realize there are many plugins and frameworks for this, but I want a simple answer.
ary.push({name: val});
where ary is a new array, name is a variable containing the key, val is the value of this entry.
I'm doing this in a jQuery loop that iterates through form fields.
In ES6...
In ES6, you can use a destructuring assignment;
ary.push({[name]: val});
However, given this is ES6 syntax, the usual caveats apply; this will not work in some browsers (noticably, IE and Edge 13)... although Babel will transpile this for you.
Without ES6 (legacy browser support)...
You need to define an object and use square bracket notation to set the property;
var obj = {};
obj[name] = val;
ary.push(obj);
If you get the urge to read into it more, see this article on the differences between square bracket and dot notation.
var ary = [];
function pushToAry(name, val) {
var obj = {};
obj[name] = val;
ary.push(obj);
}
pushToAry("myName", "myVal");
Having just fully read your question though, all you need is the following
$(your collection of form els).serializeArray();
Good old jQuery
An "associative array" is really just an object. You don't use push, you just assign properties to the object:
ary[name] = val;
The following code will help you
ary.push( {[name]: val} );
See below example
let allData = [{name: "Cat", type: "Animal"}]
let finalData: any = [];
for (let i = 0; i < allData.length; i++)
{
let obj = allData[i];
for (let KEY in obj)
{
//Pushing data to other array as object
this.finalData.push({ [KEY] : obj[KEY] });
}
}
const tStyles = [];
for (const i of iStyles) {
const temp = {};
temp[`${style}`] = `../dist/css/uikit.${wFile}.${style}.css`;
tStyles.push(temp);
}
json : {"black-beige":"../dist/css/uikit.or.black-beige.css"}