CODEWITHSUNDEEP
javascriptstring
EKR
EKR

Reputation: 187

Function that checks whether all characters in a string are equal javascript - Homework Warning

I found a solution to this homework question, but I dont feel its the most efficient way to tackle the problem. Interested in other solutions I should explore.

Question: Write a function named allEqual that returns true if every character in the string is the same

Example:

If you pass "aaa" it should return true If you pass "aba" it should return false */

My Code

var stringAE = "aba";

function allEqual(string) {
    var stringAENew = "";
    for (var i = 0; i < string.length; i++) {
        if (string[0] === string[i]) {
            stringAENew += string[i];
            console.log(stringAENew)
        }

    }
    return stringAENew === string;
}


allEqual(stringAE)

Upvotes: 6

Views: 8975

Answers (6)

developer033
developer033

Reputation: 24874

I'm a little late for the party, but as I needed to do this on a project, I came up with another approach:

function allEqual(input) {
  return input === '' || new Set(input).size === 1;
}

console.log(['', 'aaa', '11', '####', 'aba', '12', '##@%', null, undefined].map(item => ({
  item,
  allEqual: allEqual(item),
})));

Upvotes: 0

Jecoms
Jecoms

Reputation: 2848

Simple solution using .every().

function allEqual(input) {
    return input.split('').every(char => char === input[0]);
}

console.log(allEqual('aba')); // false
console.log(allEqual('aaa')); // true
console.log(allEqual('')); // true

Upvotes: 12

trincot
trincot

Reputation: 350272

This ES6 solution also works for strings with Unicode code points in other than the first plane, i.e. with codes outside of the 16 bit range:

function allEqual(string) {
    return [...string].every( (x, _, a) => x === a[0]);
}

console.log(allEqual('aaaa')); // true
console.log(allEqual('aaaba')); // false
// Next one fails in solutions that don't support multi-plane unicode:
console.log(allEqual('𝌆𝌆𝌆')); // true
console.log(allEqual('')); // true

Upvotes: 1

Mureinik
Mureinik

Reputation: 311338

There's no reason to construct a result string. Just go over all the characters and compare them to the first one (as you've been doing). If you found a different character, the result is false. If you've gone over all the characters and haven't found a different one, the answer is true (note that this includes the edge cases of an empty string and a single character string):

function allEqual(string) {
    for (var i = 1; i < string.length; i++) {
        if (string[0] !== string[i]) {
            return false;
        }

    }
    return true;
}

Upvotes: 0

Barmar
Barmar

Reputation: 781004

You can return false immediately once you find a character that doesn't match the first character. If you make it through the whole loop, return true because all the characters must have matched.

function allEqual(string) {
    for (var i = 1; i < string.length; i++) {
        if (string[i] != string[0]) {
            return false;
        }
    }
    return true;
}

You can also start your loop at i = 1, since the first character is obviously equal to itself, so there's no need to test it.

Upvotes: 3

František Žiačik
František Žiačik

Reputation: 7614

Can be done with regex too

function allEqual(str) {
   return /^(.)\1*$/.test(str);
}

Although probably not so effective.

Upvotes: 2

Related Questions