How to get length of string in javascript without using native length method

Question

I am working on a practice problem:

Return the length of a string without using javascript's native string.length method.

The only ways I could think of would be substring or slice, but I'm stumped.

Answer 1

function getStringLength(string) {
// Do NOT use any native 'length' methods.
// You might consider using 'substring' or 'slice' as alternatives.
 
  let i = 0;
  while (Number(string.slice(i, i+1)) !== 0) {
    i++;
 } return i;
}

var output = getStringLength('hello');
console.log(output); // --> 5

Answer 2

This is the solution I came up with
I have used a while loop for getting the length of the input
Sharing Two approaches with a while loop

Approach no 1

    function getLength(input) {
        if(!input){
          return 'please provide input'
        }
        let i = 0;
        while (true) {
            if (input[i]) {
                i += 1
            }else{
                break
            }
        }
        return i
    }
    
console.log(getLength([1, 5, 3, 7, 8])) // 5
console.log(getLength("Hare Krishna")) // 12

Output
5 (for array)
12 (for string)

Approach no 2

function getLength(input){
  let i = 0;
  while(input[i] !== undefined){
    i++;
  }
  return i
}

console.log(getLength([1,2,3,48,8,9])) // 6

Output
6 (for array)

Answer 3

The for in loop is the way to go I think. You can use slice or substring but for in loops can count strings easily too.

function getStringLength(string) {
      var length = 0;
      for (var i in string){
        length++;
      }
      return length;
      }

Answer 4

Yet another way to do it

function getStringLength(str){
  var count = 0;
  for(var letter in str){
    count += 1;
  }
  return count;
}

console.log(getStringLength('Mississippi')) // 11
console.log(getStringLength('')) // 0 

Answer 5

This will work.

function  length(str) {
    str = str.split(''); 
    var length = 0;
    str.forEach(function(element) { 
    length++;  
    });
    return length;    
}

length('hello'); // output 5

Answer 6

I think this will work. If you start with '', it won't go into the while loop, and you'll just return 0.

function getStringLength(string) {
  var idx = 0;
  while (string[idx] !== undefined) {
    idx += 1;
  }
  return idx;
}

Answer 7

function stringLength(str) {
  var count = 0;
  var index = 0;

  while(string[index] !== undefined){
    count += 1;
    index += 1;
  }
  return count;
}

Answer 8

The briefest have been able to achieve so far using Object.keys(), Array.prototype.pop() and checking for empty string. Approach could probably be improved further.

var len = str === "" ? 0 : +Object.keys(str).pop()+1;

---

@nnnnnnn utilizes the two methods at above far exceeding the initial attempt in brevity and addressing case of empty string.

var len = +Object.keys(str+' ').pop();

Answer 9

You can use spread element, Array.prototype.keys() iterator, Array.prototype.pop()

var str = "abc";
var len = [...[0,...str].keys()].pop();
console.log(len, str.length);

Answer 10

You could use array.length so you answer the question not using the native string.length.

var Str = "Hello world!";
const CountAr = Str.split("").length;
console.log(CountAr);
/*12*/

Answer 11

One way would be iterating through a split string like so:

var count = 0;
Array.from("string here".split("")).forEach(function(){count++});

Tip from Marko below in the comments to use the reduce function to shorten it to:

var count = Array.from("string here".split("")).reduce(function(count){return count+1}, 0);

Answer 12

You can loop over the string, testing to see whether there is a non-undefined value at each index (as soon as you get an undefined value you've run past the end of the string):

function strLength(s) {
  var length = 0;
  while (s[length] !== undefined)
    length++;
  return length;
}

console.log(strLength("Hello")); // 5
console.log(strLength("")); // 0

(I'm assuming that if you're not allowed to use the native string .length property that you probably shouldn't use the array .length property either with str.split("").length...)

Answer 13

Given that this is a practice problem, I suspect the OP may not want ES6/ES2015, but, just in case that's an option, and/or for whoever else is looking at this, here's a concise modern approach:

const str = "Hello world!";

console.log([...str].reduce(a => a+1, 0));

(When I posted this, no other answer had proposed this solution. However, I had missed the fact that @MarkoGrešak had essentially proposed this exact solution in a comment to another question.)