I'm trying to create a javascript program where I replace all spaces in a string with %20 without using the replace function. I'm getting an error when I try to run my program. Not sure what's wrong.

let urlEncode = function(text) {
  text = text.trim();
  let newstring;
  for (let i = 0; i < text.length; i++) {
    if (text[i] == " ") {
      newstring[i] = "%20";
    } else {
      newstring[i] = text[i];
    }
  }
  return newstring;
};

console.log(urlEncode("blue is greener than purple for sure"));

I'm trying to create a javascript program where I replace all spaces in a string with %20 without using the replace function. I'm getting an error when I try to run my program. Not sure what's wrong.

let urlEncode = function(text) {
  text = text.trim();
  let newstring;
  for (let i = 0; i < text.length; i++) {
    if (text[i] == " ") {
      newstring[i] = "%20";
    } else {
      newstring[i] = text[i];
    }
  }
  return newstring;
};

console.log(urlEncode("blue is greener than purple for sure"));

• javascript

• 1 what error are you getting exactly? – Prateek Commented Jan 27, 2020 at 4:29

3 Answers 3

Strings are immutable - you can't assign to their indicies. Rather, initialize newstring to the empty string, use += to concatenate the existing string with the new character(s):

let urlEncode = function(text) {
  text = text.trim();
  let newstring = '';
  for (const char of text) {
    newstring += char === ' '? '%20' : char;
  }
  return newstring;
};

console.log(urlEncode("blue is greener than purple for sure"));

Or, don't reinvent the wheel, and use encodeURIComponent:

console.log(encodeURIComponent("blue is greener than purple for sure"));

You can use bination of split and join to achieve in simplified way.

let urlEncode = function(text) {
  return text
    .trim()
    .split(" ")
    .join("%20");
};

console.log(urlEncode("blue is greener than purple for sure"));

Your Error Is first you must set newstring in first let only create your variable but not assign any value to it then newstring[0] is undefined then you get error i use += for add char to string and it is better
you can change your Code Like this

   let urlEncode = function(text) {
  text = text.trim();
  let newstring=""; 
  for (let i = 0; i < text.length; i++) {
    if (text[i] == " ") {
      newstring+= "%20";
    } else {
      newstring+= text[i];
    }
  }
return newstring;
};

console.log(urlEncode("blue is greener than purple for sure"));