TypeScript - reposition elements in an array

Question

I have following array that can have multiple elements in it.

"coachID" : [ 
     "choice1", 
     "choice2"
]

If user chooses choice2, I would like re-arrange its content as shown below.

"coachID" : [ 
     "choice2", 
     "choice1"
]

Similarly, if there are more than 2 elements in the array;

"coachID" : [ 
     "choice1", 
     "choice2",
     "choice3"
]

and user chooses choice2 element then array should be re-arranged as follows:

"coachID" : [ 
     "choice2", 
     "choice1",
     "choice3"
]

In essence, chosen element should always be placed at the beginning of the array.

How can I achieve this with TypeScript please?

Might be worthwhile tagging your question with javascript as well. I don't think there's anything typescript-specific about this. — Robby Cornelissen
– Robby Cornelissen, Commented Oct 10, 2018 at 7:46

Robby Cornelissen · Accepted Answer · 2018-10-10 09:00:39Z

2

I don't think there's anything TypeScript-specific about this.

You can just use splice() to take the selected element out, and unshift() to add it back in at the beginning:

array.unshift(...array.splice(index, 1)); // index = index of the selected element

const data = [ 
     "choice1", 
     "choice2",
     "choice3"
];

const select = (array, i) => {
  if (array && array.length && i < array.length) {
    array.unshift(...array.splice(i, 1));
  }
};

console.log(data);

select(data, 1);

console.log(data);

If you want to base the operation on the value of the selected element, add a call to indexOf():

array.unshift(...array.splice(array.indexOf(value), 1)); // value = selected value

const data = [ 
     "choice1", 
     "choice2",
     "choice3"
];

const select = (array, value) => {
  if (array && array.length) {
    const i = array.indexOf(value);
    
    if (i > 0) { 
      array.unshift(...array.splice(i, 1));
    }
  }
};

console.log(data);

select(data, "choice2");

console.log(data);

edited Oct 10, 2018 at 9:00

answered Oct 10, 2018 at 7:39

Robby Cornelissen

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3 Comments

Ali Celebi Over a year ago

I hold the value that user has selected and I want to re-arrange the array using the selected value. I'm confused as to how this solution could be used for this scenario.

Robby Cornelissen Over a year ago

So you need to find the index of the selected value first? Use indexOf().

Ali Celebi Over a year ago

Works perfect! Thanks.

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