检查字符串中所有字符是否相等的函数javascript - 作业警告

Question

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) 

Answer 1

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

Answer 2

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.

Answer 3

Can be done with regex too

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

Although probably not so effective.

Answer 4

This ES6 solution also works for strings with Unicode code points in other than the first plane , ie 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

Answer 5

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;
}

Answer 6

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), })));