What is the correct way to effectively utilize ng-bind (one-way binding) with form inputs?

Question

What is the correct way to effectively utilize ng-bind (one-way binding) with form inputs?

section, I have observed that changing the value of input2 manually and then altering the values of input1 results in input 2 not being updated any further. This raises the question: does this mean that the one-way binding in the form inputs will be disrupted if the user enters something into it?

    
    <div ng-controller="myCtrl">
        1: <input name="input1"  ng-model="topValue"/>
        2: <input name="input2"  value="{{topValue}}"/>
        topValue: <span>{{topValue}}</span>
    </div>

javascript angularjs

Answer 1

Answer №1

`ngValue` does not work with `input[text]`

According to the ngValue documentation:

The ngValue directive binds the given expression to the value of input[select] or input[radio], setting the ngModel of the element to the bound value when selected.

While debugging ngValue with input[text]:

Check in the ngValueDirective (input.js)
The $watch callback was triggered when input1 changed.
attr.$set('value',value); only changes the inner-editor (see below)
Replacing it with elm[0].value = value || ""; resolves the issue:

var ngValueDirective = function() {
  return {
    priority: 100,
    compile: function(tpl, tplAttr) {
      if (CONSTANT_VALUE_REGEXP.test(tplAttr.ngValue)) {
        return function ngValueConstantLink(scope, elm, attr) {
          attr.$set('value', scope.$eval(attr.ngValue));
        };
      } else {
        return function ngValueLink(scope, elm, attr) {
          scope.$watch(attr.ngValue, function valueWatchAction(value) {
            //attr.$set('value', value);
            elm[0].value = value || "";
          });
        };
      }
    }
  };
};

When interpolating with `value` (or any other attribute):

Angular creates $observe in the addAttrInterpolateDirective function (compile.js)
When the $observe callback is triggered, it uses attr.$set(name, newValue), leading to the same issue;

Conclusion -

Consider submitting a feature request
Or create your own custom ngValue directive.

Answer 2

`ngValue` does not work with `input[text]`

According to the ngValue documentation:

The ngValue directive binds the given expression to the value of input[select] or input[radio], setting the ngModel of the element to the bound value when selected.

While debugging ngValue with input[text]:

Check in the ngValueDirective (input.js)
The $watch callback was triggered when input1 changed.
attr.$set('value',value); only changes the inner-editor (see below)
Replacing it with elm[0].value = value || ""; resolves the issue:

var ngValueDirective = function() {
  return {
    priority: 100,
    compile: function(tpl, tplAttr) {
      if (CONSTANT_VALUE_REGEXP.test(tplAttr.ngValue)) {
        return function ngValueConstantLink(scope, elm, attr) {
          attr.$set('value', scope.$eval(attr.ngValue));
        };
      } else {
        return function ngValueLink(scope, elm, attr) {
          scope.$watch(attr.ngValue, function valueWatchAction(value) {
            //attr.$set('value', value);
            elm[0].value = value || "";
          });
        };
      }
    }
  };
};

When interpolating with `value` (or any other attribute):

Angular creates $observe in the addAttrInterpolateDirective function (compile.js)
When the $observe callback is triggered, it uses attr.$set(name, newValue), leading to the same issue;

Conclusion -

Consider submitting a feature request
Or create your own custom ngValue directive.

Answer 3

Answer №2

Absolutely. If a user modifies the content of input2, the value of input2 will no longer be recognized as an AngularJS expression, causing any alterations to topValue to go unnoticed.

Answer 4

Absolutely. If a user modifies the content of input2, the value of input2 will no longer be recognized as an AngularJS expression, causing any alterations to topValue to go unnoticed.

Answer 5

Answer №3

Summary: The binding is functional.

Expanded Explanation:

When dealing with elements, it's important to distinguish between attributes and properties. This difference is especially noticeable with attributes of an input element.

The value attribute represents the initial or default value of the element. However, once you start typing in the input field, the value attribute becomes irrelevant.

Therefore, when using an angular expression like value="{{topValue}}", the attribute's value will update whenever the expression {{topValue}} changes. Nevertheless, once the content of the input field is altered – whether manually or programmatically by modifying the value property of the input element – this attribute value becomes inconsequential.

Answer 6

Summary: The binding is functional.

Expanded Explanation:

When dealing with elements, it's important to distinguish between attributes and properties. This difference is especially noticeable with attributes of an input element.

The value attribute represents the initial or default value of the element. However, once you start typing in the input field, the value attribute becomes irrelevant.

Therefore, when using an angular expression like value="{{topValue}}", the attribute's value will update whenever the expression {{topValue}} changes. Nevertheless, once the content of the input field is altered – whether manually or programmatically by modifying the value property of the input element – this attribute value becomes inconsequential.

What is the correct way to effectively utilize ng-bind (one-way binding) with form inputs?

Answer №1

`ngValue` does not work with `input[text]`

When interpolating with `value` (or any other attribute):

Conclusion -

Answer №2

Answer №3

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What is the correct way to effectively utilize ng-bind (one-way binding) with form inputs?

Answer №1

ngValue does not work with input[text]

When interpolating with value (or any other attribute):

Conclusion -

Answer №2

Answer №3

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`ngValue` does not work with `input[text]`

When interpolating with `value` (or any other attribute):