String examples written in JavaScript

String.js

var string = "this is a nice string"
var arrayString = [ ...string.split('')]

arrayString
(21) ["t", "h", "i", "s", " ", "i", "s", " ", "a", " ", "n", "i", "c", "e", " ", "s", "t", "r", "i", "n", "g"]

arrayString.reverse()
(21) ["g", "n", "i", "r", "t", "s", " ", "e", "c", "i", "n", " ", "a", " ", "s", "i", " ", "s", "i", "h", "t"]

var newString = arrayString.toString()

console.log(newString)
// 1 g,n,i,r,t,s, ,e,c,i,n, ,a, ,s,i, ,s,i,h,t

var reversed = newString.replace(/,/g , " ");

console.log(reversed)
// 1 g n i r t s   e c i n   a   s i   s i h t


/**
** Algorithm Question - Test if string has all unique chars
**/   
// solution I - remove all duplicates and compare with original string
{
  console.log("Solution I");
  const testStringFalse = "let us go where no one goes";
  const testStringTrue = "abcdefghijklmnopqrstuvwxyz";

  function uniqueChars(string) {
      return [ ...new Set(string)];
  }

  function isUnique(string) {
      return uniqueChars(string).length === string.length;
  }

  console.log(isUnique(testStringFalse));
  console.log(isUnique(testStringTrue));
}


// solution II - array of booleans to store if ascii char already found
{
  console.log("Solution II");

  const testStringFalse = "let us go where no one goes";
  const testStringTrue = "abcdefghijklmnopqrstuvwxyz1234567890";

  function uniqueChars(string) {
      if (string.length > 128) return false;      // ascii original exceeded

      var charSet = new Array(128);
      for(var i = 0; i < string.length; i++) {
          var value = string.charAt(i);
          if(charSet[value]) return false;
          charSet[value] = true;
      }
      return true;
  }

  console.log(uniqueChars(testStringFalse));
  console.log(uniqueChars(testStringTrue));

}

// solution III compare each char with rest of string
{

  console.log("Solution III");
  const testStringFalse = "let us go where no one goes";
  const testStringTrue = "abcdefghijklmnopqrstuvwxyz1234567890";

  function uniqueChars(string) {
      for(var i = 0; i < string.length; i++) {
          var value = string.charAt(i);
          for (var j = i + 1 ; j < string.length; j++) {
              var valueTwo = string.charAt(j);
              console.log('valueOne:' + value + ' compared to: ' + valueTwo);
              if(value == valueTwo) return false;
          }
      }
      return true;
  }

  console.log(uniqueChars(testStringFalse));
  console.log(uniqueChars(testStringTrue));

}