How find a value within an array, with a users input

Question

var x1 ='&spades',
    y1 ='&clubs'
    z1 ='&hearts';
var x2 = ' ', y2 = ' ', z2 = ' ';  
var x3 = ' ', y3 = ' ', z3 = ' ';    


var Array = [x1,y1,z1,
             x2,y2,z2,
             x3,y3,z3];

Then I get an input from the user asking them to select a location (ex. x1) store it as input 1, then ask them for another location (ex. x2) and store that as input 2, and I have to swap the locations of the value.

I initially tried something like Array[input1] = Array[input2]

But Array[input1] is undefined even though input1 = x1 because Array[x1] is still undefined.

So how do I make Array[x1] = Array[0] so I can swap the values or is there an easier way?

Sorry if my question is poorly formed.

For starters, 'Array' is a keyword. Probably not a good idea to use it as a variable name. Next, the indices to your array are 0 through 9. JS has no idea how to map 'x2' to 4. — Jim B.
– Jim B., Commented Nov 12, 2018 at 4:22
use a variable to temporarily store the value of Array[firstValueToSwap] value and store the Array[secondValueToSwap] in Array[firstValueToSwap] and store the value in temp to Array[secondValueToSwap]. It's the easiest way to swap two values. BTW your question is not that clear. hope this is what you're looking for — Sanira Liyanage
– Sanira Liyanage, Commented Nov 12, 2018 at 4:25
As per my understanding, you have an array with 9 elements in it. Example: [ '&spades', '&clubs', '&hearts', ' ', ' ' , ' ' , ' ' , ' ' , ' ']. Now you want to swap the values at 2 indexes (input1 and input2) for example if the user entered 0 and 2. The new array will be [ '&hearts', '&clubs', '&spades', ' ', ' ' , ' ' , ' ' , ' ' , ' ']. I am writing this comment so that community can understand the question correctly. — Suyash Gulati
– Suyash Gulati, Commented Nov 12, 2018 at 4:30
@JimB. I know this isnt my real code my array is a lot bigger just a simple version, and I know that JS doesnt know how to map x2 to 4 but I was trying to see if there is any way otherwise i have to rewrite my program — David
– David, Commented Nov 12, 2018 at 4:30

CertainPerformance · Accepted Answer · 2018-11-12 04:25:27Z

2

Assuming the inputs are strings ('x1' and 'x2'), you need a way to represent the variable names in your data structure. One way would be to have, rather than an array of strings, an array of objects, containing a label and a value property. Then, just find the indicies of both labels for both inputs, and reassign those indicies.

Also, better not to assign to a variable named Array, because that will shadow the global Array object - name it something else instead, like arr:

const arr = [
  { label: 'x1', value: '&spades' },
  { label: 'y1', value: '&clubs' },
  { label: 'z1', value: '&hearts' }
  // ...
];
// Inputs:
const label1 = 'x1';
const label2 = 'y1';

// Calculate indicies:
const [index1, index2] = [label1, label2].map(
  findLabel => arr.findIndex(({ label }) => label === findLabel)
);
([arr[index1], arr[index2]] = [arr[index2], arr[index1]]);
console.log(arr);

The destructuring line at the end there allows for swapping variables in two positions at once, without having to resort to an intermediate variable:

([arr[index1], arr[index2]] = [arr[index2], arr[index1]]);

If you find that confusing, an alternative is to actually use an intermediate variable:

const orig1 = arr[index1];
arr[index1] = arr[index2];
arr[index2] = orig1;

answered Nov 12, 2018 at 4:25

CertainPerformance

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2 Comments

David Over a year ago

I will try this as soon as I get back home, I see what you mean, I used a very very simple version of my code as an example of what I was trying to do I know not to name it array was just example but I will try to implement this method into my own code will let you know how it goes, thank you

David Over a year ago

Yes, thank you @CertainPerformance, by making my array of objects now allows me to make the connection between the array and users input so now I can switch them, at the bottom I get a bit fuzzy on how the whole switching works, I just used some if statements with an intermediate var because I didnt understand what the bottom half was doing. Though I will try to play around to try and understand it. Thank you for your help.

Jim B. · Accepted Answer · 2018-11-12 04:37:14Z

0

Here's what your code might look like if you use an object:

    let arr = {};
    arr['x1'] = '&spades';
    arr['y1'] = '&clubs';
    arr['z1'] = '&hearts';
    arr['x2'] = ' ';
    arr['y2'] = ' ';
    arr['z2'] = ' ';
    arr['x3'] = ' ';
    arr['y3'] = ' ';
    arr['z3'] = ' ';
    
    console.log(arr['z1']);
    arr['z1'] = 'foo';
    console.log(arr['z1']);

answered Nov 12, 2018 at 4:37

Jim B.

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2 Comments

David Over a year ago

I see what you mean now CertainPerformace was saying something about the same will try as soon as I can, thank you

David Over a year ago

Yes, @JimB. you were right the answer was that I had to make an array of objects. Thank you for your help.

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