JavaScript string replace is not working

Question

I am writing a program which takes three parameters e.g, sentence, wordtoreplace, toReplaceWith.

program should return sentence string with wordtoreplace should be replaced with toReplaceWith. And if the wordtoreplace is a capitalized word then the replaced world should also be capitalized. I tried many times but my code doesn't work. Help please.

function myReplace(str, before, after) {
  var words = str.split(" ");
  var indexOfWord = words.indexOf(before);
  
    if ( before.charAt(0) === before.charAt(0).toUpperCase ) {
      after = capitalize(after);
    }
   str = str.replace(new RegExp(before), after);
   
      function capitalize( word ) {
      return word.charAt(0).toUpperCase() + word.slice(1);
      }
   return str.replace(new RegExp(after, 'i', 'g'), after);;
}

myReplace("A quick brown fox jumped over the lazy dog", "jumped", "leaped");

Why do you split the string in words? Note that RegExp does not take three arguments. You need to call toUpperCase() with parentheses. You don't use words or indexOfWord once they are initialised. Why do you have them? But it seems a bit redundant to apply the capitalisation when the caller of your function could easily provide the capital letter? It makes the function non-user-friendly. — trincot
– trincot, Commented Jan 14, 2017 at 19:39

Charlie L · Accepted Answer · 2017-01-14 19:20:43Z

1

You should probably invoke toUpperCase within your if statement

if ( before.charAt(0) === before.charAt(0).toUpperCase() ) { after = capitalize(after); }

answered Jan 14, 2017 at 19:20

Charlie L

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fingerprints · Accepted Answer · 2017-01-14 19:44:02Z

1

Try this:

function myReplace(str, before, after) {
  var words = str.split(" ");
  var indexOfWord = words.indexOf(before);

  if ( before.charAt(0) == before.charAt(0).toUpperCase() ) {
     after = capitalize(after);
  }
  str = str.replace(new RegExp('\\b' + before + '\\b'), after);

  function capitalize( word ) {
    return word.charAt(0).toUpperCase() + word.slice(1);
  }
  return str.replace(new RegExp(after, 'i', 'g'), after);;
}

You can use '\\b' for find in the string. You can test the code here: http://www.w3schools.com/code/tryit.asp?filename=FBQS72BU7H97

Here the doc: http://www.w3schools.com/jsref/jsref_regexp_begin.asp

answered Jan 14, 2017 at 19:44

fingerprints

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1 Comment

J Akhtar Over a year ago

sorry but it is not working if the the before starts with an uppercase letter it doesn't replace with after.

Martin Greilinger · Accepted Answer · 2017-01-14 20:09:57Z

0

You missed the parenthesis at the .toUpperCase() function in your if statement.

I have also tried to make your version a bit cleaner, maybe it will help you.

function replace(sentence, wordToReplaced, newWord) {
  if (sentence.includes(wordToReplaced)) {
    var char = wordToReplaced.charAt(0);
    if (char === char.toUpperCase()) {
      newWord = newWord.charAt(0).toUpperCase() + newWord.slice(1);
    }
    sentence = sentence.replace(wordToReplaced, newWord);
  }
  return sentence;
}

answered Jan 14, 2017 at 20:09

Martin Greilinger

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