Loop through looped sequence of numbers

Question

There is an array of numbers [1,2,3,4,5,6,7,8,9,10]

I need to get all numbers from this sequence that are different from current for more than 2 items, but looped.

For example if current number is one, so new list should have everything except 9,10,1,2,3, or if current number is four so new list should be everything except 2,3,4,5,6.

Is there any technique how to make this, without creating multiple loops for items at start and at the end?

Thank you.

• Florent: Can you provide more examples?
• Marvin3: Added one more example, hope it's more clear now.
• Chris: is the array always the same? If nto does it always loop on 10? does it always contain consecutive elements, etc. Should the order they are returned be the same as the original array or is order irrelevant?
• Marvin3: New order should be the same, but without those numbers. Length of array and number of items is dynamic (it can be array with 25 items, or with 300). And it's always consecutive.

Answer 1

var a = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; 
var exclude = function (start, distance, array) { 
 var result = []; 
 for (var i = 0; i < array.length; i++) { 
 var d = Math.min( 
 Math.abs(start - i - 1), 
 Math.abs(array.length + start - i - 1)
 ) 
 if (d > distance) { 
 result.push(array[i]); 
 } 
 } 
 return result; 
} 

• Marvin3: Thank you. Your method is the fastest one.
• Marvin3: I just changed to 'd > distance' as I need items in new array to be already exluded.

Answer 2

I think this performs what you asked:

// Sorry about the name
function strangePick(value, array) {
 var n = array.length
 , i = array.indexOf(value);
 if (i >= 0) {
 // Picked number
 var result = [value];
 // Previous 2 numbers
 result.unshift(array[(i + n - 1) % n]);
 result.unshift(array[(i + n - 2) % n]);
 // Next 2 numbers
 result.push(array[(i + 1) % n]);
 result.push(array[(i + 2) % n]);
 return result;
 } else {
 return [];
 }
}

Some tests:

var array = [1,2,3,4,5,6,7,8,9,10];
console.log(strangePick(1, array)); // [9,10,1,2,3]
console.log(strangePick(4, array)); // [2,3,4,5,6]

Answer 3

You may use javascript array.slice:

function get_offset_sequence(arr, index, offset) {
 var result = [];
 if (index - offset < 0) {
 result = arr.slice(index - offset).concat(arr.slice(0, index + offset + 1));
 }
 else if (index + offset > arr.length - 1) {
 result = arr.slice(index - offset).concat(arr.slice(0, Math.abs(arr.length - 1 - index - offset)));
 }
 else {
 result = arr.slice(index - offset, index + offset + 1)
 }
 return result;
 }

Example of use:

var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var index = 1;
var offset = 2;
for (var i=0; i < 10; i++) { console.log(i, arr[i], get_offset_sequence(arr, i, offset)) }