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Using AngularJS directive to format input field while leaving scope variable unchanged

Posted by: admin November 29, 2017 Leave a comment

Questions:

I’m having an issue formatting an input field, while leaving the underlying scope variable non-formatted.

What I want to achieve is a text field to display currency. It should format itself on the fly, while handling wrong input. I got that working, but my problem is that I want to store the non-formatted value in my scope variable. The issue with input is that it requires a model which goes both ways, so changing the input field updates the model, and the other way around.

I came upon $parsers and $formatters which appears to be what I am looking for. Unfortunately they are not affecting each other (which might actually be good to avoid endless loops).

I’ve created a simple jsFiddle: http://jsfiddle.net/cruckie/yE8Yj/ and the code is as follows:

HTML:

<div data-ng-app="app" data-ng-controller="Ctrl">
    <input type="text" data-currency="" data-ng-model="data" />
    <div>Model: {{data}}</div>
</div>

JS:

var app = angular.module("app", []);

function Ctrl($scope) {
    $scope.data = 1234567;
}

app.directive('currency', function() {
    return {
        restrict: 'A',
        require: 'ngModel',
        link: function (scope, element, attr, ctrl) {

            ctrl.$formatters.push(function(modelValue) {
                return modelValue.toString().replace(/\B(?=(?:\d{3})+(?!\d))/g, ',');
            });

            ctrl.$parsers.push(function(viewValue) {
                return parseFloat(viewValue.replace(new RegExp(",", "g"), ''));
            });
        }
    };
});

Again, this is just a simple example. When it loads everything looks as it’s supposed to. The input field is formatted and the variable is not. However, when changing the value in the input field it no longer formats itself – the variable however gets updated correctly.

Is there a way to ensure the text field being formatted while the variable is not? I guess what I am looking for is a filter for text fields, but I can’t seen to find anything on that.

Best regards

Answers:

Here’s a fiddle that shows how I implemented the exact same behavior in my application. I ended up using ngModelController#render instead of $formatters, and then adding a separate set of behavior that triggered on keydown and change events.

http://jsfiddle.net/KPeBD/2/

Questions:
Answers:

I have refactored the original directive, so that it uses $parses and $formatters instead of listening to keyboard events. There is also no need to use $browser.defer

See working demo here http://jsfiddle.net/davidvotrubec/ebuqo6Lm/

    var myApp = angular.module('myApp', []);

    myApp.controller('MyCtrl', function($scope) {
      $scope.numericValue = 12345678;
    });

    //Written by David Votrubec from ST-Software.com
    //Inspired by http://jsfiddle.net/KPeBD/2/
    myApp.directive('sgNumberInput', ['$filter', '$locale', function ($filter, $locale) {
            return {
                require: 'ngModel',
                restrict: "A",
                link: function ($scope, element, attrs, ctrl) {
                    var fractionSize = parseInt(attrs['fractionSize']) || 0;
                    var numberFilter = $filter('number');
                    //format the view value
                    ctrl.$formatters.push(function (modelValue) {
                        var retVal = numberFilter(modelValue, fractionSize);
                        var isValid = isNaN(modelValue) == false;
                        ctrl.$setValidity(attrs.name, isValid);
                        return retVal;
                    });
                    //parse user's input
                    ctrl.$parsers.push(function (viewValue) {
                        var caretPosition = getCaretPosition(element[0]), nonNumericCount = countNonNumericChars(viewValue);
                        viewValue = viewValue || '';
                        //Replace all possible group separators
                        var trimmedValue = viewValue.trim().replace(/,/g, '').replace(/`/g, '').replace(/'/g, '').replace(/\u00a0/g, '').replace(/ /g, '');
                        //If numericValue contains more decimal places than is allowed by fractionSize, then numberFilter would round the value up
                        //Thus 123.109 would become 123.11
                        //We do not want that, therefore I strip the extra decimal numbers
                        var separator = $locale.NUMBER_FORMATS.DECIMAL_SEP;
                        var arr = trimmedValue.split(separator);
                        var decimalPlaces = arr[1];
                        if (decimalPlaces != null && decimalPlaces.length > fractionSize) {
                            //Trim extra decimal places
                            decimalPlaces = decimalPlaces.substring(0, fractionSize);
                            trimmedValue = arr[0] + separator + decimalPlaces;
                        }
                        var numericValue = parseFloat(trimmedValue);
                        var isEmpty = numericValue == null || viewValue.trim() === "";
                        var isRequired = attrs.required || false;
                        var isValid = true;
                        if (isEmpty && isRequired) {
                            isValid = false;
                        }
                        if (isEmpty == false && isNaN(numericValue)) {
                            isValid = false;
                        }
                        ctrl.$setValidity(attrs.name, isValid);
                        if (isNaN(numericValue) == false && isValid) {
                            var newViewValue = numberFilter(numericValue, fractionSize);
                            element.val(newViewValue);
                            var newNonNumbericCount = countNonNumericChars(newViewValue);
                            var diff = newNonNumbericCount - nonNumericCount;
                            var newCaretPosition = caretPosition + diff;
                            if (nonNumericCount == 0 && newCaretPosition > 0) {
                                newCaretPosition--;
                            }
                            setCaretPosition(element[0], newCaretPosition);
                        }
                        return isNaN(numericValue) == false ? numericValue : null;
                    });
                } //end of link function
            };
            //#region helper methods
            function getCaretPosition(inputField) {
                // Initialize
                var position = 0;
                // IE Support
                if (document.selection) {
                    inputField.focus();
                    // To get cursor position, get empty selection range
                    var emptySelection = document.selection.createRange();
                    // Move selection start to 0 position
                    emptySelection.moveStart('character', -inputField.value.length);
                    // The caret position is selection length
                    position = emptySelection.text.length;
                }
                else if (inputField.selectionStart || inputField.selectionStart == 0) {
                    position = inputField.selectionStart;
                }
                return position;
            }
            function setCaretPosition(inputElement, position) {
                if (inputElement.createTextRange) {
                    var range = inputElement.createTextRange();
                    range.move('character', position);
                    range.select();
                }
                else {
                    if (inputElement.selectionStart) {
                        inputElement.focus();
                        inputElement.setSelectionRange(position, position);
                    }
                    else {
                        inputElement.focus();
                    }
                }
            }
            function countNonNumericChars(value) {
                return (value.match(/[^a-z0-9]/gi) || []).length;
            }
            //#endregion helper methods
        }]);

Github code is here [https://github.com/ST-Software/STAngular/blob/master/src/directives/SgNumberInput]

Questions:
Answers:

I’ve revised a little what Wade Tandy had done, and added support for several features:

  1. thousands separator is taken from $locale
  2. number of digits after decimal points is taken by default from $locale, and can be overridden by fraction attribute
  3. parser is activated only on change, and not on keydown, cut and paste, to avoid sending the cursor to the end of the input on every change
  4. Home and End keys are also allowed (to select the entire text using keyboard)
  5. set validity to false when input is not numeric, this is done in the parser:

            // This runs when we update the text field
        ngModelCtrl.$parsers.push(function(viewValue) {
            var newVal = viewValue.replace(replaceRegex, '');
            var newValAsNumber = newVal * 1;
    
            // check if new value is numeric, and set control validity
            if (isNaN(newValAsNumber)){
                ngModelCtrl.$setValidity(ngModelCtrl.$name+'Numeric', false);
            }
            else{
                newVal = newValAsNumber.toFixed(fraction);
                ngModelCtrl.$setValidity(ngModelCtrl.$name+'Numeric', true);
            }
            return newVal;
    
        });
    

You can see my revised version here – http://jsfiddle.net/KPeBD/64/

Questions:
Answers:

Indeed the $parsers and $formatters are “independent” as you say (probably for loops, again as you say). In our application we explicitly format with the onchange event (inside the link function), roughly as:

element.bind("change", function() {
    ...
    var formattedModel = format(ctrl.$modelValue);
    ...
    element.val(formattedModel);
});

See your updated fiddle for the detailed and working example: http://jsfiddle.net/yE8Yj/1/

I like binding to the onchange event, because I find it annoying to change the input as the user is typing.

Questions:
Answers:

The fiddle is using an old version of angular(1.0.7).

On updating to a recent version, 1.2.6, the $render function of the ngModelCtrl is never called, meaning if the model value is changed in the controller,

the number is never formatted as required in the view.

//check if new value is numeric, and set control validity
if (isNaN(newValAsNumber)){
  ngModelCtrl.$setValidity(ngModelCtrl.$name+'Numeric', false);
}

Here is the updated fiddle http://jsfiddle.net/KPeBD/78/

Questions:
Answers:

Based on the answer from Wade Tandy here is a new jsfiddle with following improvements:

  • decimal numbers possible
  • thousands separator and decimal separator based on locals
  • and some other tweaks …

I have also replaces all String.replace(regex) by split().join(), because this allows me to use variables in the expression.

http://jsfiddle.net/KPeBD/283/