Javascript Interview Question String Get the first non-repeated character

Introduction

Write an efficient function to find the first non-repeated character in a String. 

function findFirstNonRepeatedChar(str) {
    //your code//from   w  w  w. j a  v a 2  s. co m
}

console.log( findFirstNonRepeatedChar('lorem ipsum dolar pit ahmets') );

/*
Output: ($ /usr/bin/node 001.js)
u
*/



/**
 * @function {public static} findFirstNonRepeatedChar
 *
 * Finds the first non-repeated character of a given `String`.
 *
 * @param {String} str - the `String` to seek.
 *
 * @return the first non-repeated character if found, `null` otherwise.
 */
function findFirstNonRepeatedChar(str) {
    var charHash = {};
    var i = 0;
    var c = '';
    var o = null;
    var len = str.length;

    var kSeenOnce = 1;
    var kSeenTwice = 2;

    for (i = 0; i < len; i++) {
        c = str[i];
        o = charHash[c];

        if (o === undefined) {
            charHash[c] = kSeenOnce;
        } else if (o === kSeenOnce) {
            charHash[c] = kSeenTwice;
        }
    }

    for (i = 0; i < len; i++) {
        c = str[i];

        if (charHash[c] === kSeenOnce) {
            return c;
        }
    }

    return null;
}

console.log( findFirstNonRepeatedChar('lorem ipsum dolar pit ahmets') );

/*
Output: ($ /usr/bin/node 001.js)
u
*/



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