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- directive in module ng
select element with AngularJS data-binding.
select directive is used together with ngModel to provide data-binding between the scope and the
<select> control (including setting default values). It also handles dynamic
<option> elements, which can be added using the ngRepeat or ngOptions directives.
When an item in the
<select> menu is selected, the value of the selected option will be bound to the model identified by the
ngModel directive. With static or repeated options, this is the content of the
value attribute or the textContent of the
<option>, if the value attribute is missing. Value and textContent can be interpolated.
The select controller exposes utility functions that can be used to manipulate the select's behavior.
Matching model and option values
In general, the match between the model and an option is evaluated by strictly comparing the model value against the value of the available options.
If you are setting the option value with the option's
value attribute, or textContent, the value will always be a
string which means that the model value must also be a string. Otherwise the
select directive cannot match them correctly.
To bind the model to a non-string value, you can use one of the following strategies:
- the ngOptions directive (select)
- the ngValue directive, which allows arbitrary expressions to be option values (Example)
- model $parsers / $formatters to convert the string value (Example)
If the viewValue of
ngModel does not match any of the options, then the control will automatically add an "unknown" option, which it then removes when the mismatch is resolved.
Optionally, a single hard-coded
<option> element, with the value set to an empty string, can be nested into the
<select> element. This element will then represent the
null or "not selected" option. See example below for demonstration.
Choosing between ngRepeat and ngOptions
In many cases,
ngRepeat can be used on
<option> elements instead of ngOptions to achieve a similar result. However,
ngOptions provides some benefits:
- more flexibility in how the
<select>'s model is assigned via the
selectas part of the comprehension expression
- reduced memory consumption by not creating a new scope for each repeated instance
- increased render speed by creating the options in a documentFragment instead of individually
Specifically, select with repeated options slows down significantly starting at 2000 options in Chrome and Internet Explorer / Edge.
- This directive executes at priority level 0.
<select ng-model="string" [name="string"] [multiple="string"] [required="string"] [ng-required="string"] [ng-change="string"] [ng-options="string"] [ng-attr-size="string"]> ... </select>
||Assignable AngularJS expression to data-bind to.|
||Property name of the form under which the control is published.|
||Allows multiple options to be selected. The selected values will be bound to the model as an array.|
||Adds required attribute and required validation constraint to the element when the ngRequired expression evaluates to true. Use ngRequired instead of required when you want to data-bind to the required attribute.|
||AngularJS expression to be executed when selected option(s) changes due to user interaction with the select element.|
||sets the options that the select is populated with and defines what is set on the model on selection. See ngOptions.|
||sets the size of the select element dynamically. Uses the ngAttr directive.|
Simple select elements with static options
Using ngRepeat to generate select options
Using ngValue to bind the model to an array of objects
Using select with ngOptions and setting a default value
See the ngOptions documentation for more
ngOptions usage examples.
Binding select to a non-string value via ngModel parsing / formatting
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