# Yahoo! UI Library

### datatype 3.0.0b1

Yahoo! UI Library > datatype > datatype-number-format.js (source view)
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    /**
     * Number submodule.
     *
     * @module datatype
     * @submodule datatype-number
     */

    /**
     * Format number submodule.
     *
     * @module datatype
     * @submodule datatype-number-format
     */

    /**
     * DataType.Number provides a set of utility functions to operate against Number objects.
     *
     * @class DataType.Number
     * @static
     */
    var LANG = Y.Lang;

    Y.mix(Y.namespace("DataType.Number"), {
         /**
         * Takes a Number and formats to string for display to user.
         *
         * @method format
         * @param data {Number} Number.
         * @param config {Object} (Optional) Optional configuration values:
         *  <dl>
         *   <dt>prefix {String}</dd>
         *   <dd>String prepended before each number, like a currency designator "$"</dd>
         *   <dt>decimalPlaces {Number}</dd>
         *   <dd>Number of decimal places to round. Must be a number 0 to 20.</dd>
         *   <dt>decimalSeparator {String}</dd>
         *   <dd>Decimal separator</dd>
         *   <dt>thousandsSeparator {String}</dd>
         *   <dd>Thousands separator</dd>
         *   <dt>suffix {String}</dd>
         *   <dd>String appended after each number, like " items" (note the space)</dd>
         *  </dl>
         * @return {String} Formatted number for display. Note, the following values
         * return as "": null, undefined, NaN, "".
         */
        format: function(data, config) {
            if(LANG.isNumber(data)) {
                config = config || {};

                var isNeg = (data < 0),
                    output = data + "",
                    decPlaces = config.decimalPlaces,
                    decSep = config.decimalSeparator || ".",
                    thouSep = config.thousandsSeparator,
                    decIndex,
                    newOutput, count, i;

                // Decimal precision
                if(LANG.isNumber(decPlaces) && (decPlaces >= 0) && (decPlaces <= 20)) {
                    // Round to the correct decimal place
                    output = data.toFixed(decPlaces);
                }

                // Decimal separator
                if(decSep !== "."){
                    output = output.replace(".", decSep);
                }

                // Add the thousands separator
                if(thouSep) {
                    // Find the dot or where it would be
                    decIndex = output.lastIndexOf(decSep);
                    decIndex = (decIndex > -1) ? decIndex : output.length;
                    // Start with the dot and everything to the right
                    newOutput = output.substring(decIndex);
                    // Working left, every third time add a separator, every time add a digit
                    for (count = 0, i=decIndex; i>0; i--) {
                        if ((count%3 === 0) && (i !== decIndex) && (!isNeg || (i > 1))) {
                            newOutput = thouSep + newOutput;
                        }
                        newOutput = output.charAt(i-1) + newOutput;
                        count++;
                    }
                    output = newOutput;
                }

                // Prepend prefix
                output = (config.prefix) ? config.prefix + output : output;

                // Append suffix
                output = (config.suffix) ? output + config.suffix : output;

                return output;
            }
            // Not a Number, just return as string
            else {
                Y.log("Could not format data " + Y.dump(data) + " from type Number", "warn", "datatype-number");
                return (LANG.isValue(data) && data.toString) ? data.toString() : "";
            }
        }
    });

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