Determine if a string has all Unique Characters

<script>

// Javascript program to illustrate string with
// unique characters using brute force
// technique
function uniqueCharacters(str)
{
    
    // If at any time we encounter 2
    // same characters, return false
    for(let i = 0; i < str.length; i++)
        for(let j = i + 1; j < str.length; j++)
            if (str[i] == str[j])
                return false;

    // If no duplicate characters
    // encountered, return true
    return true;
}

// Driver code
let input = "GeeksforGeeks";

if (uniqueCharacters(input) == true)
    document.write("The String " + input + 
                   " has all unique characters" + "</br>");
else
    document.write("The String " + input + 
                   " has duplicate characters");
                 
// This code is contributed by decode2207

</script>

<script>

    // Javascript program to 
    // check string with unique
    // characters using sorting technique
    
    /* Convert the string to character array
    for sorting */
    function uniqueCharacters(str)
    {
        let chArray = str.split('');
 
        // Using sorting
        chArray.sort();
 
        for (let i = 0; i < chArray.length - 1; i++) 
        {
 
            // if the adjacent elements are not
            // equal, move to next element
            if (chArray[i] != chArray[i + 1])
                continue;
 
            // if at any time, 2 adjacent elements
            // become equal, return false
            else
                return false;
        }
 
        return true;
    }
    
    let input = "GeeksforGeeks";
 
    if (uniqueCharacters(input) == true)
      document.write("The String " + input + 
      " has all unique characters" + "</br>");
    else
      document.write("The String " + input + 
      " has duplicate characters" + "</br>");
    
</script>

<script>
    // Javascript program to illustrate String With
    // Unique Characters using data structure
    
    let MAX_CHAR = 256;
 
    function uniqueCharacters(str)
    {
        // If length is greater than 256,
        // some characters must have been repeated
        if (str.length > MAX_CHAR)
            return false;
 
        let chars = new Array(MAX_CHAR);
        for (let i = 0; i < MAX_CHAR; i++) {
            chars[i] = false;
        }
        for (let i = 0; i < str.length; i++) {
            let index = str[i].charCodeAt();
 
            /* If the value is already true, string
            has duplicate characters, return false */
            if (chars[index] == true)
                return false;
 
            chars[index] = true;
        }
 
        /* No duplicates encountered, return true */
        return true;
    }
    
    let input = "GeeksforGeeks";

    if (uniqueCharacters(input))
      document.write("The String " + input
                        + " has all unique characters");
    else
      document.write("The String " + input
                        + " has duplicate characters");
    
</script>

<script>
    // Javascript program to illustrate String
    // with unique characters without
    // using any data structure
    
    function uniqueCharacters(str)
    {
        // Assuming string can have
        // characters a-z this has
        // 32 bits set to 0
        let checker = 0;
 
        for (let i = 0; i < str.length; i++) {
            let bitAtIndex = str[i].charCodeAt(0) - 'a'.charCodeAt(0);
 
            // if that bit is already set
            // in checker, return false
            if ((checker & (1 << bitAtIndex)) > 0) {
                return false;
            }
 
            // otherwise update and continue by
            // setting that bit in the checker
            checker = checker | (1 << bitAtIndex);
        }
 
        // no duplicates encountered,
        // return true
        return true;
    }
    
    let input = "geekforgeeks";
 
    if (uniqueCharacters(input)) {
      document.write("The String " + input + " has all unique characters");
    }
    else {
      document.write("The String " + input + " has duplicate characters");
    }
    
</script>

// JavaScript code to implement the approach

function uniqueCharacters(s)
{
    // If at any character more than once create another
    // stream stream count more than 0, return false
    let arr = s.split("");
    return !arr.some((v, i) => arr.indexOf(v) < i);
}

let input = "GeeksforGeeks";

if (uniqueCharacters(input))
    console.log("The String " + input + " has all unique characters");
else
    console.log("The String " + input + " has duplicate characters");




// This code is contributed by phasing17

<script>

// Function program to illustrate String 
// with unique characters
function uniqueCharacters(str)
{
    
    // Converting string to set
    var setstring = new Set(str)
    
    // If length of set is equal to len of string
    // then it will have unique characters
    if (setstring.size == str.length)
    {
        return true
    }
    else
    { 
        return false
    }
}

// Driver Code
var input = "GeeksforGeeks"

if (uniqueCharacters(input))
{
    document.write("The String " + input +
                   " has all unique characters") ;
}
else
{
    document.write("The String " + input +
                   " has duplicate characters")
}

// This code is contributed by bunnyram19

</script>