fastest way to detect if duplicate entry exists in javascript array?

Question

var arr = [\'test0\',\'test2\',\'test0\'];

Like the above,there are two identical entries with value \"test0\",how to check it most efficiently?

Answer 1

You can convert the array to to a Set instance, then convert to an array and check if the length is same before and after the conversion.

const hasDuplicates = (array) => {
  const arr = ['test0','test2','test0'];
  const set1 = new Set(array);
  const uniqueArray = [...set1];
  
  return array.length !== uniqueArray.length;
};

console.log(`Has duplicates : ${hasDuplicates(['test0','test2','test0'])}`);
console.log(`Has duplicates : ${hasDuplicates(['test0','test2','test3'])}`);