Currency Format Input Field

currency-format-input-field.markdown

Currency Format Input Field

Auto format currency input field with commas and decimals if needed. This is how I would personally expect one to work. Works left to right without forcing user to enter 00 cents if there is none. Text is automatically formatted with commas and cursor is placed back where user left off after formatting vs cursor moving to the end of the input. Validation is on KeyUp and a final validation is done on blur.

A Pen by Wade Williams on CodePen.

License.

index.html

<div class="main">
  <h1>Auto Formatting Currency</h1>
  
  <form method="post" action="#">
  <label for="currency-field">Enter Amount</label>
  <input type="text" name="currency-field" id="currency-field" pattern="^\$\d{1,3}(,\d{3})*(\.\d+)?$" value="" data-type="currency" placeholder="$1,000,000.00">
  <button type="submit">Submit</button>
</form>

<p>Auto format currency input field with commas and decimals if needed. Text is automatically formated with commas and cursor is placed back where user left off after formatting vs cursor moving to the end of the input. Validation is on KeyUp and a final validation is done on blur.</p>

<p>To use just add the following to an input field:</p>
  
 <pre>data-type="currency"</pre>
  
</div><!-- /main -->

script.js

// Jquery Dependency

$("input[data-type='currency']").on({
    keyup: function() {
      formatCurrency($(this));
    },
    blur: function() { 
      formatCurrency($(this), "blur");
    }
});


function formatNumber(n) {
  // format number 1000000 to 1,234,567
  return n.replace(/\D/g, "").replace(/\B(?=(\d{3})+(?!\d))/g, ",")
}


function formatCurrency(input, blur) {
  // appends $ to value, validates decimal side
  // and puts cursor back in right position.
  
  // get input value
  var input_val = input.val();
  
  // don't validate empty input
  if (input_val === "") { return; }
  
  // original length
  var original_len = input_val.length;

  // initial caret position 
  var caret_pos = input.prop("selectionStart");
    
  // check for decimal
  if (input_val.indexOf(".") >= 0) {

    // get position of first decimal
    // this prevents multiple decimals from
    // being entered
    var decimal_pos = input_val.indexOf(".");

    // split number by decimal point
    var left_side = input_val.substring(0, decimal_pos);
    var right_side = input_val.substring(decimal_pos);

    // add commas to left side of number
    left_side = formatNumber(left_side);

    // validate right side
    right_side = formatNumber(right_side);
    
    // On blur make sure 2 numbers after decimal
    if (blur === "blur") {
      right_side += "00";
    }
    
    // Limit decimal to only 2 digits
    right_side = right_side.substring(0, 2);

    // join number by .
    input_val = "$" + left_side + "." + right_side;

  } else {
    // no decimal entered
    // add commas to number
    // remove all non-digits
    input_val = formatNumber(input_val);
    input_val = "$" + input_val;
    
    // final formatting
    if (blur === "blur") {
      input_val += ".00";
    }
  }
  
  // send updated string to input
  input.val(input_val);

  // put caret back in the right position
  var updated_len = input_val.length;
  caret_pos = updated_len - original_len + caret_pos;
  input[0].setSelectionRange(caret_pos, caret_pos);
}

scripts

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>

style.css

html {
  box-sizing: border-box;
}

*, *:before, *:after {
  box-sizing: inherit;
}


body {
  background: #f5f5f5;
  color: #333;
  font-family: arial, helvetica, sans-serif;
  font-size: 32px;
}

h1 {
  font-size: 32px;
  text-align: center;
}

p {
  font-size: 20px;
  line-height: 1.5;
  margin: 40px auto 0;
  max-width: 640px;
}

pre {
  background: #eee;
  border: 1px solid #ccc;
  font-size: 16px;
  padding: 20px;
}

form {
  margin: 40px auto 0;
}

label {
  display: block;
  font-size: 24px;
  font-weight: bold;
  margin-bottom: 10px;
}

input {
  border: 2px solid #333;
  border-radius: 5px;
  color: #333;
  font-size: 32px;
  margin: 0 0 20px;
  padding: .5rem 1rem;
  width: 100%;

}

button {
  background: #fff;
  border: 2px solid #333;
  border-radius: 5px;
  color: #333;
  font-size: 16px;
  font-weight: bold;
  padding: 1rem;
}

button:hover {
  background: #333;
  border: 2px solid #333;
  color: #fff;
}

.main {
  background: #fff;
  border: 5px solid #ccc;
  border-radius: 10px;
  margin: 40px auto;
  padding: 40px;
  width: 80%;
  max-width: 700px;
}