how to convert numbers to strings and push them into an array in JavaScript?

Question

I was solving an exercise with array methods; where I was expected to input a number and the returned value should be the same number with dashes between each two consecutive even numbers.

I have wrote this code so far but It's returning an empty array, It would be much better if you could point out my mistakes than giving an alternative solution.

function dashit(num){ 
   //test num = 025468, expected arr = ["0","-","2","5","4","-","6","-  ","8"]
    var arr = [];
    var prog = num.toString().split(""); // I suppose ["0","2","5","4","6","8"]
    for (var i = 0; i<num.length; i = i + 2){
        if (num[i] % 2 == 0 ){ // case of "0" and "2"
            if (num[i+1] % 2 == 0){
                arr.push(prog[i]); // "0" pushed from prog to arr
                arr.push("-");     // "-" pushed from prog to arr
                arr.push(prog[i+1]); // "2" pushed from prog to arr
            }
        }
        else { // case of "5" and "4"
                arr.push(prog[i]);  // "5" pushed from prog to arr
                arr.push(prog[i+1]); // "4" pushed from prog to arr
        }
    }
    return arr;
}

I suppose num is an actual number (as in the comment), and num[i] doesn't make sense, but your debugger will tell you everything you need to know — Amit
– Amit, Commented Mar 17, 2016 at 22:28
num.length is undefined. Did you mean prog.length? Same with all the other num uses. Why are you using num in same cases and prog in others? — Felix Kling
– Felix Kling, Commented Mar 17, 2016 at 22:28
If you know num contains just numbers, you could use parseInt(num) to get an integer. If it could contain some junk characters, a /(\d+)/ regex may be more suitable. Is there any reason you're rolling your own solution? — Tibrogargan
– Tibrogargan, Commented Mar 17, 2016 at 22:30
You are using javascript strings like C strings- they are not. To extract a specific character use substring() method, however in your code prog is an array of characters, you are using num which is still an integer. — Arif Burhan
– Arif Burhan, Commented Mar 17, 2016 at 22:30
Then you should learn how to debug JavaScript ASAP! Otherwise, how you will be able to verify or fix your code? — Felix Kling
– Felix Kling, Commented Mar 17, 2016 at 22:31

DCruz22 · Accepted Answer · 2016-03-17 22:30:25Z

2

You are comparing your num var, you have to compare the prog var :

    function dashit(num){ 
    var prog = num.toString().split(""); // I suppose ["0","2","5","4","6","8"]
    for (var i = 0; i<prog.length; i = i + 2){
        if (prog[i] % 2 == 0 ){ // case of "0" and "2"
            if (prog[i+1] % 2 == 0){
}

answered Mar 17, 2016 at 22:30

DCruz22

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1 Comment

DCruz22 Over a year ago

Always willing to help :D

isvforall · Accepted Answer · 2016-03-17 23:16:47Z

1

You are passing num as octal number(starts with 0)

Try pass it as a string

dashit("025468");

See working example:

function dashit(num){ 
  
    var arr = [];
    
    for (var i = 0; i<num.length; i = i + 2){
        if (num[i] % 2 == 0 ){ // case of "0" and "2"
            if (num[i+1] % 2 == 0){
                arr.push(num[i]); // "0" pushed from prog to arr
                arr.push("-");     // "-" pushed from prog to arr
                arr.push(num[i+1]); // "2" pushed from prog to arr
            }
        }
        else { // case of "5" and "4"
                arr.push(num[i]);  // "5" pushed from prog to arr
                arr.push(num[i+1]); // "4" pushed from prog to arr
                arr.push("-");
        }
    }
    return arr;
} 


document.write(JSON.stringify(dashit("025468")));

edited Mar 17, 2016 at 23:16

answered Mar 17, 2016 at 22:29

isvforall

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2 Comments

Mohamed Hegazy Over a year ago

thanks alot for your input, it actually worked but for some reason only 1 dash is missing between 4 and 6

isvforall Over a year ago

@MohamedHegazy you forget add arr.push("-"); in else statement, I've updated the code, please see

Thomas E · Accepted Answer · 2016-03-18 10:27:58Z

0

This problem is perfect for the use of recursion. I'm certain that's what your teacher wanted ;-)

var n = '02546878642';

var isPair = function(n1, n2) {
  return Number(n1) % 2 == 0 && Number(n2) % 2 == 0;
};

var result = (function f(i, o) {

  if (i.length < 1) return o;
  var first = i.shift();
  var next =  i[0];
  o.push(first);
  if (isPair(first, next)) {
    o.push('-');
  }
  return f(i, o);
})(n.split(''), []);



$('#result').html(result.join(''));

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id='result'>result</div>

answered Mar 18, 2016 at 10:27

Thomas E

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