Most efficient way to replace string with emoji

Question

What is the most efficient way to replace text like :) -> .

So, assume I have a text like "Hello :) my name is Alex". I should convert the text into "Hello my name is Alex"

I solved this issue with help of lodash utility library.

const replaceStringWithEmoji = (string) => {
  const emojiMap = {
    ':)': '',
    ':(': '',
    ':D': '',
    ';(': '',
    ':O': '',
    ';)': '',
    '8)': '',
    '>:@': '',
  };

  const emojis = [...Object.keys(emojiMap)];
  return _.join(_.map(_.split(string, ' '), (s) => {
    if (_.includes(emojis, s)) {
      return emojiMap[s];
    }
    return s;
  }), ' ');
};

There has to be a better way of doing it. Maybe with Regex?

Short return

 return _.join(_.map(_.split(string, ' '), s => _.includes(emojis, s) ? emojiMap[s] : s), ' ');

If your code works well and there is no issue, please consider posting the question at [codereview.se]. — Wiktor Stribiżew, Sep 18 '19 at 07:32
Seems like you need to hardset the majority of this data. Not sure what much more you would like to get this to perform better. :) — Chris Ngo, Sep 18 '19 at 07:35
This question is quite open ended. What does 'efficient' and 'better' mean in your situation? If your code is readable and works for all required test cases then do not fall into a trap of doing pre-mature optimisation. — ethane, Sep 18 '19 at 07:36

score 6 · Accepted Answer · answered Sep 18 '19 at 07:35

I'd construct a pattern by taking the keys, escaping all the special characters, and joining by |. Then replace by looking up the matched string on the object:

const escape = s => s.replace(/[-\/\\^$*+?.()|[\]{}]/g, '\\$&');

const replaceStringWithEmoji = (string) => {
  const emojiMap = {
    ':)': '',
    ':(': '',
    ':D': '',
    ';(': '',
    ':O': '',
    ';)': '',
    '8)': '',
    '>:@': '',
  };
  const pattern = new RegExp(
    Object.keys(emojiMap).map(escape).join('|'),
    'g'
  );
  return string.replace(pattern, match => emojiMap[match]);
};

console.log(replaceStringWithEmoji('foo :) bar'));
console.log(replaceStringWithEmoji('foo :) bar 8) baz'));

score 4 · Answer 2 · answered Sep 18 '19 at 07:35

4

You don't need to change your emojiMap to array you can build a regex with alternation and use repalce

const replaceStringWithEmoji = (string) => {
  const emojiMap = {
    ':)': '',
    ':(': '',
    ':D': '',
    ';(': '',
    ':O': '',
    ';)': '',
    '8)': '',
    '>:@': '',
  };
  let regex = /(?::\)|:\(|:D|;\(|:O'|;\)|8\)|>:@)/g
  return string.replace(regex,(m)=>emojiMap[m] || m)
};

console.log(replaceStringWithEmoji("Hello :) my name is Alex"))

answered Sep 18 '19 at 07:35

Code Maniac

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Is string.replace() typically O(n)? Upvoted btw – Chris Ngo Sep 18 '19 at 07:39
2

@ChristopherNgo as far as i know it depends on your regex, since this regex doesn't include any backtracking so it should be `O( m + n )` where m is length of input and n is number of alternation – Code Maniac Sep 18 '19 at 07:42
Sweet! Good to know :) – Chris Ngo Sep 18 '19 at 07:43

Most efficient way to replace string with emoji

2 Answers2