How to determine if a string contains a sequence of repeated letters

Question

Using JavaScript, I need to check if a given string contains a sequence of repeated letters, like this:

"aaaaa"

How can I do that?

Answer 1

This will check if the string has repeats more than twice:

function checkStr(str) {
    str = str.replace(/\s+/g,"_");
    return /(\S)(\1{2,})/g.test(str);
}

Answer 2

You can use this function:

function hasRepeatedLetters(str) {
    var patt = /^([a-z])\1+$/;
    var result = patt.test(str);
    return result;
}

Answer 3

Use regular expressions:

var hasDuplicates = (/([a-z])\1/i).test(str)

Or if you don't want to catch aA and the likes

var hasDuplicates = (/([a-zA-Z])\1/).test(str)

Or, if you've decided you want to clarify your question:

var hasDuplicates = (/^([a-zA-Z])\1+$/).test(str)

Answer 4

Try using this

checkRepeat = function (str) {
    var repeats = /(.)\1/;
    return repeats.test(str)
}

Sample usage

if(checkRepeat ("aaaaaaaa"))
alert('Has Repeat!')

Answer 5

function check(str) {
    var tmp = {};
    for(var i = str.length-1; i >= 0; i--) {
        var c = str.charAt(i);
        if(c in tmp) {
            tmp[c] += 1;
        }
        else {
            tmp[c] = 1;
        }
    }
    var result = {};
    for(c in tmp) {
        if(tmp.hasOwnProperty(c)) {
            if(tmp[c] > 1){
                result[c] = tmp[c];
            }
        }
    }
    return result;
}

then you can check the result to get the repeated chars and their frequency. if result is empty, there is no repeating there.