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Thread: Unusual/difficult substring extraction

  1. #1
    Join Date
    Jan 2018
    Posts
    2

    Unusual/difficult substring extraction

    Hello,
    I need to extract a substring of varying length from strings of varying lengths. I know this sounds confusing so I'll post a few examples...

    Possible strings:
    "This is a short string with a small price - $1.25"
    "This is a somewhat longer string that happens to end with a greater price - $12.45"
    "And this is just another string with a large price at the end - $1200.35"

    Somehow I need to extract just the number from each string (including the decimal point, but without the "$").
    The number I need is always at the end of the string but the range is 0.01 to 9999.99

    In the end, I will be adding these numbers together, then displaying the total as a dollar amount.

    Is this even possible? Can the "$" be used as the starting point (+1) of the substring? Can this be extracted right to left, stopping at the "$" somehow?

    Can someone provide a snippet if this isn't too complicated? Or maybe just point me in the right direction?

    Thanks,
    ---Frank

  2. #2
    Join Date
    Dec 2012
    Posts
    1,609
    Yes, this can be done easily by use of a regular expression:
    Code:
            var strings = [
                "This is a short string with a small price - $1.25",
                "This is a somewhat longer string that happens to end with a greater price - $12.45",
                "And this is just another string with a large price at the end - $1200.35"
            ];
            var result = 0;
            strings.forEach(function (item, idx) {
                matches = item.match(/\$([0-9]+\.[0-9]{2})$/);
                console.log(matches);
                result += parseFloat(matches[1]);
            });
            console.log(result);
    You can use this tester to get explanation of the regex:
    https://regex101.com

  3. #3
    Join Date
    Aug 2016
    Posts
    114
    Code:
    <!Doctype html>
    <script>
    
    a="This is a short string with a small price - $1.25"
    b="This is a somewhat longer string that happens to end with a greater price - $12.45"
    c="And this is just another string with a large price at the end - $1200.35"
    
    document.write(a,"<br>")
    document.write(a.split(" - $")[1],"<br>")
    
    </script>
    displays this output ...
    This is a short string with a small price - $1.25
    1.25
    Last edited by shakazorba; 01-16-2018 at 10:32 AM.

  4. #4
    Join Date
    Dec 2005
    Location
    TX
    Posts
    7,931

    Lightbulb

    'Sempervivum' gives a much shorter solution,
    but here is some alternate code that uses array extensively.
    You could combine the various functions and statements into one function, if desired.

    I broke the code into individual statements to make it, hopefully, easier to understand. Uses .map(), .filter() and .reduce() for examples demos

    Code:
    <!DOCTYPE html>
    <html lang="en">
    <head>
    <meta charset="UTF-8" />
    <title> HTML5 page </title>
    </head>
    <body>
    <div id="debug"></div>
    
    <script>
    // From: http://www.webdeveloper.com/forum/showthread.php?368319-Unusual-difficult-substring-extraction
    
    // demonstration string created with (`) backticks
    var statements = `This is a short string with a small price - $1.25
    This is a somewhat longer string that happens to end with a greater price - $12.45
    And this is just another string with a large price at the end - $1200.35`;
    
    var words = statements.split(/\s|\n/g);  // create array of all words in statement
    // document.getElementById('debug').innerHTML = words.join('<br>');     // for testing
    
    function getAmounts(cost) { return (cost.indexOf('$') != -1); }
    
    var amounts = words.filter(getAmounts);  // create another array of just words with '$' in them
    // document.getElementById('debug').innerHTML = amounts.join('<br>');   // for testing
    
    function stripDollar(str) { return str.replace('$',''); }  // remove '$' character from words
    var costs = amounts.map(stripDollar);
    document.getElementById('debug').innerHTML += costs.join('<br>')+'<p>';  // for testing
    
    function getSum(total, num) { return Number(total) + Number(num); }
    var sum = costs.reduce(getSum);  // form total from cost amounts
    document.getElementById('debug').innerHTML += sum;                      // for testing
    
    </script>
    </body>
    </html>

  5. #5
    Join Date
    Mar 2011
    Posts
    125
    Another solution:
    Code:
    string.substr(string.indexOf('$') + 1);

  6. #6
    Join Date
    Jan 2018
    Posts
    2
    Amazing responses! I'll try some of them out tonight and post my results.
    Thanks to all again for helping me with this.
    ---Frank

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