Question

After seeing Google’s april fools joke of the morse code gmail, I thought I’d try to create a real-time morse code converter in javascript.

I’m using regex and replace to change the morse code into character. For example:

.replace(/.- /g, "a").replace(/.-. /g, "r")

The issue I’m having is that when I’m typing .-. for “r” it give me an “a” because it sees .- first.
How can I make it replace only exact matches?

Updated and working!! Thanks to every one that helped me

http://jsfiddle.net/EnigmaMaster/sPDHL/32/ – My Original code

http://jsfiddle.net/EnigmaMaster/LDKKE/6/ – Rewritten by Shawn Chin

http://jsfiddle.net/EnigmaMaster/y9A4Y/2/ – Rewritten by Matthias Tylkowski

If anyone has other ways of writting this program please post a JsFiddle

Id love to see how else this can be done

Answer 1

The other answers have already covered the reasons why your example was not working so I’ll refrain from repeating them.

However, may I suggest that since you’re already using spaces to delimit each code, a straight-forward solution would be to do a simple .split() to segment the input text into individual units then simply do a one-to-one mapping of code to chars.
This will be a lot more efficient than repeated regex replacements and less prone to errors.

For example:

var morse = {  // use object as a map
    '.-': 'a', 
    '-...': 'b', 
    '-.-.': 'c', 
    // .... the rest ...
};

function translate_morse(code) {  // given code, return matching char
    return (typeof morse[code] === "undefined") ? "" : morse[code];
    // if the var is not found, the code is unknown/invalid. Here we 
    // simply ignore it but you could print out the code verbatim and use
    // different font styles to indicate an erroneous code
}

// example usage
translated = code_text.split(" ").map(translate_morse).join("");

Here’s a working example: http://jsfiddle.net/KGVAm/1/

p.s. I’ve taken the liberty of tweaking the code and the behaviour a little, i.e. disabling the input of other chars but allowing backscape to allow corrections.