"Enumerating" a string with a custom sequence of numbers?

Question

I am writing a function letters(text) that takes a string with uneven number of characters and makes a dictionary that gives each letter a numerical value based on their place in the string. Instead of enumerating the letters with their index, this function gives them values starting from -(lengthOfString/2) to (lengthOfString/2) so that middle character is always zero.

>>>letters("stack")
{"S": -2, "T": -1, "A": 0, "C": 1, "K": 2}

I am fairly new to JavaScript and even tough my code does its job, I don't think it is the right way to do it. Also I need to check if the text only contains letters, has an uneven amount of letters and doesn't include the same letter twice. I couldn't find a way to throw an assertion error and how to formulate the last condition.

function letters(text){

    text= text.toUpperCase();
    if(text.length % 2 !== 1 && /^[a-zA-Z]+$/.test(text)){

    }
    const len = text.length;
    const limit = parseInt(len/2);
    var list = text.split("");
    var dict = {};

    for (let j = -limit; j<=limit; j++){
        list.push(j)
    }
    for (var range = 0; range < list.length/2;range++ ) {
        dict[list[range]] = [];
        dict[list[range]].push(list[range + list.length / 2]);
    }
  
    return dict
}
console.log(letters("stack"))

What happens if there are repeated characters, eg ann? Or is that not an input that will be encountered for this problem? — CertainPerformance
– CertainPerformance, Commented Apr 21, 2020 at 4:00
The function won't accept the input and throw an Assertion Error that says "invalid text" — arty
– arty, Commented Apr 21, 2020 at 4:10

Nilanka Manoj · Accepted Answer · 2020-04-21 04:14:53Z

2

You can simply:

const letters = (txt) => {
  if(txt.length%2==0){throw "even length exeption";return}
  let out = {}
  for (var x = 0; x < txt.length; x++)
  {
    out[txt.charAt(x)] = x - (txt.length-1)/2
    
  }
  return out
}

console.log(letters('stack'))
console.log(letters('stackk'))

edited Apr 21, 2020 at 4:14

answered Apr 21, 2020 at 4:09

Nilanka Manoj

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Code Maniac · Accepted Answer · 2020-04-21 04:18:33Z

2

You can add test for repeated words using Set and also can remove the last loop

function letters(text) {
  text = text.toUpperCase();
  let repeated = new Set([...text]).size !== text.length
  if ( text.length % 2 === 0 || /[^A-Z]/.test(text) || repeated) {
    return "Invalid text"
  }

  const limit = parseInt(text.length / 2);
  var dict = {};

  for (let j = -limit, range = 0; range < text.length; j++, range++) {
    dict[text[range]] = j
  }
  return dict
}
console.log(letters("stack"))
console.log(letters("Ana"))

edited Apr 21, 2020 at 4:18

answered Apr 21, 2020 at 4:13

Code Maniac

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