Reverse stack filling with javascript

Question

how do i add each of the contents of array_A, into the last empty position of array_B. So basically, i'm trying to fill the array from the top of the stack, down, using the contents of another array...if that makes sense.

function PopulateArrayDown() {

//Declare an empty array and its size
var myArray = [];
myArray.length = 10;

//Get last index 
var lastElement =myArray.length;

//Create array of data
var Data = [1, 2, 3, 4, 5];

//For each value in data, add it to last position in myArray
$.each(Data, function (lastElement, value) {
    myArray.push(lastElement, value);
    lastElement -1;

});

So after this i hoped to see at [10] : 1, at [9] : 2, at [8] : 3 ect.. Fail! lastElement seemed to get reset to 0 as soon as the code got into the .each()

check for a null or empty value in the array. If it is empty or null insert your value from array B. — snowYetis
– snowYetis, Commented Oct 2, 2014 at 19:29
Would i not need to know the index of that empty element first? to ensure im inserting the new value at the top most element in the array — Sophie Maiden
– Sophie Maiden, Commented Oct 2, 2014 at 20:27

Nicolas Albert · Accepted Answer · 2014-10-02 20:11:24Z

1

If you want a reverse version of an array, here a simple code:

var Data = [1, 2, 3, 4, 5];
var myArray = Data.slice(0, Data.length).reverse(); // make a copy and reverse
myArray; // [5, 4, 3, 2, 1];

If you want your code to work:

//Declare an empty array and its size
var myArray = [];
myArray.length = 10;

//Get last index 
var lastElement = myArray.length - 1;

//Create array of data
var Data = [1, 2, 3, 4, 5];

//For each value in data, add it to last position in myArray
$.each(Data, function (id, value) {
    myArray[lastElement] = value;
    lastElement--;
});
myArray; // [undefined × 5, 5, 4, 3, 2, 1]

if you array length is 10, the last index is 9 (length - 1)
$.each function first argument is an index, don't put the same name of the variable you need to access
lastElement - 1 does nothing, but lastElement-- is like lastElement-=1 like lastElement = lastElement - 1

edited Oct 2, 2014 at 20:11

answered Oct 2, 2014 at 19:37

Nicolas Albert

2,5961 gold badge18 silver badges18 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Sophie Maiden Over a year ago

Aah, now i see. Thanks for explaining Nick :)

Nicolas Albert Over a year ago

Good, you can validate the answer now :-)

DaaaahWhoosh · Accepted Answer · 2014-10-02 19:45:09Z

0

You don't need to use jQuery for such a simple problem. I would recommend something like this:

var myArray = [];
myArray.length = 10;
var Data = [1, 2, 3, 4, 5];
var lastElement =myArray.length;
for (var i=0; i< Data.length; i++){
  myArray[lastElement-i] = Data[i];
}

This assumes Data and Array have the same number of elements, which sounds like what you wanted.

edited Oct 2, 2014 at 19:45

answered Oct 2, 2014 at 19:33

DaaaahWhoosh

3891 gold badge4 silver badges15 bronze badges

2 Comments

Johan Over a year ago

for..in is intended to be used on object properties, not arrays.

Sophie Maiden Over a year ago

That for loop on first glance looks pretty intense, but kinda makes sense. Think i just need to try an read through it to understand it. Also, I'm going to try an add another (3rd) array values into the remaining empty elements using this and push.

Hema Anumolu · Accepted Answer · 2014-10-02 19:49:43Z

0

var a=[1,2,3,4,5,6];
var b =[9,56,46,34,78,97];var j =1;
for(i=a.length-1;i>-1;i--){
b[b.length+j]=a[i];
j++;
}
console.log(b);

[9, 56, 46, 34, 78, 97, 7: 6, 10: 5, 14: 4, 19: 3, 25: 2, 32: 1]

answered Oct 2, 2014 at 19:49

Hema Anumolu

1711 silver badge2 bronze badges

Comments

LL1138 · Accepted Answer · 2014-10-02 20:05:59Z

0

Javascript arrays can be made to work like lists, or stacks, or queues, whatever you need. Use push to append and unshift to prepend items. So your code could look like

var myArray = [],
    Data = [1, 2, 3, 4, 5];

for(var i=0; i<Data.length; i++) {
    myArray.unshift(Data[i]);
}

answered Oct 2, 2014 at 20:05

LL1138

1263 bronze badges

1 Comment

Sophie Maiden Over a year ago

Great tip thanks LL, im really getting into javascript/jquery so this is great.

Collectives™ on Stack Overflow

Reverse stack filling with javascript

4 Answers 4

2 Comments

2 Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

2 Comments

2 Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related