JSFiddle - React, Tailwind, and code Playground

JavaScript

function combine(arr) {
	var combinations = [];
  
	for(i = 0; i < arr.length; i++) {
  	for(j=i+1; j < arr.length; j++) {
  		combinations.push([arr[i], arr[j]]);
    }
  }
  
  return combinations;
}

console.log(JSON.stringify(combine([1, 2, 3, 4, 5])));