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Push a dimensional array

Why the answer is undefined in the Second example?
// First
var arr = [
[1, 4, 6],
['alex']
];
var newArr = arr[1];
newArr.push('Peter');
console.log(arr);
// Second
var arr = [
[1, 4, 6],
['alex']
];
arr.push([1]['Peter']);
console.log(arr);

The code [1]['Peter'] is trying to access a key named Peter from the array literal [1]. And it is undefined
Your code is equivalent to this:
var arr = [
[1, 4, 6],
['alex']
];
var tempArray = [1];
var tempValue = tempArray['Peter'] // undefined
arr.push(tempValue);
console.log(arr);
You should change it to: arr[1].push('Peter')

That syntax [1]['Peter'] doesn't do what you might imagine. You're passing an input parameter. It doesn't reference the array pushing it into, it's completely independent. So you're effectively telling JavaScript to first create a new array ([1]), and then try to access an index called "Peter" from within it (["Peter"]), and then push that into the next free index in arr. Clearly that "Peter" index doesn't exist within the new array, which is why it outputs undefined.
Instead you'd have to write it like this, so it pushes to the existing array, which is itself at index 1 of arr:
// First
var arr = [
[1, 4, 6],
['alex']
];
var newArr = arr[1];
newArr.push('Peter');
console.log(arr);
// Second
var arr = [
[1, 4, 6],
['alex']
];
arr[1].push('Peter');
console.log(arr);

The problem is
arr.push([1]['Peter']);
But an array which contains a single element, 1, does not have the property Peter. Arrays generally do not have non-numeric properties (other than those on Array.prototype and Object.prototype)

All you need to do is
var arr = [
[1, 4, 6],
['alex']
];
arr[1].push('Peter');
console.log(arr);

Union which mutate array in lodash

Is there a function in lodash which makes a union of two arrays by modifying the first one? Union should add the element only if there are no duplicates.
Something along the lines of
a=[1,2,3,4,5,6]; _.mergeArrays(a, [6,7]);
[1,2,3,4,5,6,7]

This can be easily done with "vanilla" JavaScript. It requires ES5 (2009) only, which is implemented by all the major web browsers.
var array = [1,2,3,4,5];
var anotherArray = [6,7];
anotherArray.forEach(function(val) {
if (array.indexOf(val) === -1) {
array.push(val);
}
});

You can use spread element, Set which does not allow duplicate entries
var a = [1, 2, 3, 4, 5];
var add = [6, 7, 3, 5];
a = [...new Set([...a, ...add])];
console.log(a);

Reducing array of items into a single array list [duplicate]

This question already has answers here:
Merge/flatten an array of arrays
(84 answers)
Closed 6 years ago.
Below is my array if items that I want to reduce it to a single list of arrays..
var input=[
[
2
],
[
3,
13
],
[
4,
14
],
[
5,
15,
25,
35
]
]
var output=[
2,
3,
13,
4,
14,
5,
15,
25,
35
]
My code:
function reduceArray(item){
for(var i=0;i<item.length;i++){
return i;
}
}
var result=result.map((item)=>{
if(item.length>0){
return reduceArray(item);
}else{
return item;
}
})
which produces the same result.Can anyone please figure out where I'm doing wrong or any other approach to achieve this..Thanks

input.reduce(function(a, x) { return a.concat(x); });
// => [2, 3, 13, 4, 14, 5, 15, 25, 35]
reduce sets the accumulator to the first element (or a starting value if provided), then calls the function with the accumulator and each successive element. The function we provide is concatenation. If we say input is [a, b, c], then the above command will be equivalent to a.concat(b).concat(c). [concat](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/concat) produces a new array by smushing two or more arrays together.
EDIT: Actually, there is another possible answer:
Array.prototype.concat.apply(input[0], array.slice(1));
// => [2, 3, 13, 4, 14, 5, 15, 25, 35]
This directly calls concat with multiple arguments; if input is again [a, b, c], then this is equivalent to a.concat(b, c). apply calls a function with a given receiver and arguments; slice will give us just a part of the array, in this case everything starting from the first element (which we need to chop off since it needs to be the receiver of the concat call).

One liner would be
input = [[2],[3,13],[4,14],[5,15,25,35]];
[].concat.apply([],input);

You can use lodash's flattenDeep()
_.flattenDeep([1, [2, [3, [4]], 5]]);
// → [1, 2, 3, 4, 5]

User concat.check this for more information http://www.w3schools.com/jsref/jsref_concat_array.asp
var input=[[2],[3,13],[4,14],[5,15,25,35]];
var output=[];
for(var i = 0; i < input.length; i++)
{
output = output.concat(input[i]);
}
console.log(output);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

use concat is the perfect way
The concat() method is used to join two or more arrays.
This method does not change the existing arrays, but returns a new array, containing the values of the joined arrays.
var newArr = [];
for(var i = 0; i < input.length; i++)
{
newArr = newArr.concat(input[i]);
}
console.log(newArr);

Javascript:: Find differences between array that contains duplicated values to a unique array of that array

I found many posts on stack overflow about that similar subject but none of them solve this issue here.
<script>
//Array GanginaA contains duplicated values.
//Array GanginaB contains only unique values that have been fetched from GanginaA
GanginaA=[0,1,2,3,4,5,5,6,7,8,9,9];
GanginaB=[0,1,2,3,4,5,6,7,8,9];
var hezi=<!--The Magic Goes Here-->
console.log(hezi);
/*
* Expected Output:
* 5,9
*/
</script>
GanginaA will always be longer or identical to GanginaB so there is no reason to calculate by the value of the longer array length.
GanginaB will always contains unique values that taken from GanginaA so it will always be the shorter array length or identical to GanginaA array.
Now it makes it a lot easier to find doubles.

You can use filter to get the elements like below
GanginaA = [0, 1, 2, 3, 4, 5, 5, 6, 7, 8, 9, 9];
GanginaB = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
var hezi = GanginaB.filter(function (item, index) {
return GanginaA.indexOf(item) !== GanginaA.lastIndexOf(item)
});
console.log(hezi.join(" , ")); // 5, 9

the easier I can think of :
var hezi=[];
for (var i=0;i<GanginaA.length;i++){
hezi[GanginaA[i]] = GanginaA[i];
hezi[GanginaB[i]] = GanginaB[i];
}
hezi = hezi.filter (function(el){return el!=undefined;});
does everything in O(n) actions and not O(n^2)

Javascript's objects have hashmap like behaviour, so you can use them kind of like a set. If you iterate over all the values and set them to be keys within an object, you can use the Object.keys method to get an array of unique values out.
function uniqueValues() {
var unique = {};
[].forEach.call(arguments, function(array) {
array.forEach(function(value) {
unique[value] = true;
});
});
return Object.keys(unique);
};
This function will return the unique elements in any number of arrays, passed as arguments.
uniqueValues([1, 2, 3], [ 1, 1, 1], [2, 2, 2], [3, 3, 3]); // [ 1, 2 3 ]
One drawback to this method is that Javascript coerces all keys to strings, you can turn them back into numbers by changing the return statement to:
return Object.keys(unique).map(Number);

Retrieving a property of a JSON object by index?

Assuming this JSON object:
var obj = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
The "set2" property may be retrieved like so:
obj["set2"]
Is there a way to retrieve the "set2" property by index? It is the second property of the JSON object. This does not work (of course):
obj[1]
So, let's say that I want to retrieve the second property of the JSON object, but I don't know its name - how would I do it then?
Update: Yes, I understand that objects are collections of unordered properties. But I don't think that the browsers mess with the "original" order defined by the JSON literal / string.

Objects in JavaScript are collections of unordered properties. Objects are hashtables.
If you want your properties to be in alphabetical order, one possible solution would be to create an index for your properties in a separate array. Just a few hours ago, I answered a question on Stack Overflow which you may want to check out:
Iterating over a JavaScript object in sort order based on particular key value of a child object
Here's a quick adaptation for your object1:
var obj = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
var index = [];
// build the index
for (var x in obj) {
index.push(x);
}
// sort the index
index.sort(function (a, b) {
return a == b ? 0 : (a > b ? 1 : -1);
});
Then you would be able to do the following:
console.log(obj[index[1]]);
The answer I cited earlier proposes a reusable solution to iterate over such an object. That is unless you can change your JSON to as #Jacob Relkin suggested in the other answer, which could be easier.
1 You may want to use the hasOwnProperty() method to ensure that the properties belong to your object and are not inherited from Object.prototype.

I know this is an old question but I found a way to get the fields by index.
You can do it by using the Object.keys method.
When you call the Object.keys method it returns the keys in the order they were assigned (See the example below). I tested the method below in the following browsers:
Google Chrome version 43.0
Firefox version 33.1
Internet Explorer version 11
I also wrote a small extension to the object class so you can call the nth key of the object using getByIndex.
// Function to get the nth key from the object
Object.prototype.getByIndex = function(index) {
return this[Object.keys(this)[index]];
};
var obj1 = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
var obj2 = {
"set2": [4, 5, 6, 7, 8],
"set1": [1, 2, 3],
"set3": [9, 10, 11, 12]
};
log('-- Obj1 --');
log(obj1);
log(Object.keys(obj1));
log(obj1.getByIndex(0));
log('-- Obj2 --');
log(obj2);
log(Object.keys(obj2));
log(obj2.getByIndex(0));
// Log function to make the snippet possible
function log(x) {
var d = document.createElement("div");
if (typeof x === "object") {
x = JSON.stringify(x, null, 4);
}
d.textContent= x;
document.body.appendChild(d);
}

No, there is no way to access the element by index in JavaScript objects.
One solution to this if you have access to the source of this JSON, would be to change each element to a JSON object and stick the key inside of that object like this:
var obj = [
{"key":"set1", "data":[1, 2, 3]},
{"key":"set2", "data":[4, 5, 6, 7, 8]},
{"key":"set3", "data":[9, 10, 11, 12]}
];
You would then be able to access the elements numerically:
for(var i = 0; i < obj.length; i++) {
var k = obj[i]['key'];
var data = obj[i]['data'];
//do something with k or data...
}

Simple solution, just one line..
var obj = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
obj = Object.values(obj);
obj[1]....

Here you can access "set2" property following:
var obj = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
var output = Object.keys(obj)[1];
Object.keys return all the keys of provided object as Array..

Jeroen Vervaeke's answer is modular and the works fine, but it can cause problems if it is using with jQuery or other libraries that count on "object-as-hashtables" feature of Javascript.
I modified it a little to make usable with these libs.
function getByIndex(obj, index) {
return obj[Object.keys(obj)[index]];
}

You could iterate over the object and assign properties to indexes, like this:
var lookup = [];
var i = 0;
for (var name in obj) {
if (obj.hasOwnProperty(name)) {
lookup[i] = obj[name];
i++;
}
}
lookup[2] ...
However, as the others have said, the keys are in principle unordered. If you have code which depends on the corder, consider it a hack. Make sure you have unit tests so that you will know when it breaks.

"""
This could be done in python as follows.
Form the command as a string and then execute
"""
context = {
"whoami": "abc",
"status": "0",
"curStep": 2,
"parentStepStatus": {
"step1":[{"stepStatus": 0, "stepLog": "f1.log"}],
"step2":[{"stepStatus": 0, "stepLog": "f2.log"}]
}
}
def punc():
i = 1
while (i < 10):
x = "print(" + "context" + "['parentStepStatus']" + "['%s']"%("step%s")%(i) + ")"
exec(x)
i+=1
punc()

There is no "second property" -- when you say var obj = { ... }, the properties inside the braces are unordered. Even a 'for' loop walking through them might return them in different orders on different JavaScript implementations.

it is quite simple...
var obj = {
"set1": [1, 2, 3],
"set2": [4, 5, 6, 7, 8],
"set3": [9, 10, 11, 12]
};
jQuery.each(obj, function(i, val) {
console.log(i); // "set1"
console.log(val); // [1, 2, 3]
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

var obj = {
"set1": [
1,
2,
3
],
"set2": [
4,
5,
6,
7,
8
],
"set3": [
9,
10,
11,
12
]
};
var outputKeys = Object.keys(obj)[1];
var outputValues = Object.values(obj)[1];
//outputKeys would be "set2"`enter code here`
//outPutValues would be [4,5,6,7,8]

My solution:
Object.prototype.__index=function(index)
{var i=-1;
for (var key in this)
{if (this.hasOwnProperty(key) && typeof(this[key])!=='function')
{++i;
}
if (i>=index)
{return this[key];
}
}
return null;
}
aObj={'jack':3, 'peter':4, '5':'col', 'kk':function(){alert('hell');}, 'till':'ding'};
alert(aObj.__index(4));