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 t

Answer 1

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 2

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.

Answer 3

var char = "abcbdf..,,ffffd,,,d,,,";
var tempArry={};

for (var i=0; i < char.length; i++) {
    if (tempArry[char[i]]) {
        tempArry[char[i]].push(char[i]);
    } else {
        tempArry[char[i]] = [];
        tempArry[char[i]].push(char[i]);
    }
}

console.log(tempArry);

This will even return the number of repeated characters also.

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

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 6

I solved that using a for loop, not with regex

//This check if a string has 3 repeated letters, if yes return true, instead return false
//If you want more than 3 to check just add another validation in the if check

function stringCheck (string) {
    for (var i = 0; i < string.length; i++)
        if (string[i]===string[i+1] && string[i+1]===string[i+2]) 
            return true
    
    return false 	
}
var str1 = "hello word" //expected false
var str2 = "helllo word" //expredted true
var str3 = "123 blAAbA" //exprected false
var str4 = "hahaha haaa" //exprected true

console.log(str1, "<==", stringCheck(str1))
console.log(str2, "<==", stringCheck(str2))
console.log(str3, "<==", stringCheck(str3))
console.log(str4, "<==", stringCheck(str4))