JSFiddle - React, Tailwind, and code Playground

JavaScript

var arr = [1, 7, 2, 3, 2, 1, 4, 5, 5, 1];

function unique(array) {
  let seen = {};
  let result = [];
  
  for (let value of array) {
    if (!seen[value]) {
	    seen[value] = 1;
  	  result.push(value);
    }
  }

  return result;
}

alert(unique(arr)); // 1,7,2,3,4,5