ng-options how to set first select always blank

问题

I am using angularjs in a project and in which I am using ng-options for generating .

Initially when the pages reload and no option element is selected the html generated like below:

<select size="3" ng-model="item" ng-options="s.name for s in itemlist">
<option value="?" selected="selected"></option>
<option value="0">Item 1</option>
<option value="1">Item 2</option>
<option value="2">Item 3</option>
</select>

But when I select an element (ex. Item 2) the first blank select is gone. I know its happening as ng-model is being set by select value. But I want first select always blank so that user can reset the filter.

Thanks in advance.

回答1:

This will do the work for you:

<select size="3" ng-model="item" ng-options="s.name for s in itemlist">
    <option value="">Select Option</option>
</select>

回答2:

For anyone out there that treat "null" as valid value for one of the options (so imagine that "null" is a value of one of the items in typeOptions in example below), I found that simplest way to make sure that automatically added option is hidden is to use ng-if.

<select ng-options="option.value as option.name for option in typeOptions">
    <option value="" ng-if="false"></option>
</select>

Why ng-if and not ng-hide? Because you want css selectors that would target first option inside above select to target "real" option, not the one that's hidden. It gets useful when you're using protractor for e2e testing and (for whatever reason) you use by.css() to target select options.

Kevin - Sưu Tầm

回答3:

You can forgo using the ng-options and use ng-repeat instead and make the first option blank. See example below.

<select size="3" ng-model="item">
    <option value="?" selected="selected"></option>
    <option ng-repeat="s in itemlist" value="{{s.value}}">{{s.name}}</option>
</select>

回答4:

It appears that your best option would be to have the blank item included as the first item in itemlist.

回答5:

The solution above will corrupt the model with junk data. Please use the directive to reset the model in the right way JS: Select Option

Directive"
 .directive('dropDown', function($filter) {
    return {

        require: 'ngModel',
        priority: 100,
        link: function(scope, element, attr, ngModel) {

            function parse(value) {

                if (value) {

                    if(value === "")
                    {
                        return "crap"
                    }
                    else
                    {
                        return value;
                    }

                } else {
                    return;
                }
            }


            ngModel.$parsers.push(parse);

        }
    };
});

回答6:

        <select ng-model="dataItem.platform_id"
            ng-options="item.id as item.value for item in platformList"
            ng-init="dataItem.platform_id=dataItem.platform_id||platformList[0].id"></select>

回答7:

Controller

$scope.item = '';

$scope.itemlist = {
   '' = '',
   'Item 0' = 1,
   'Item 1' = 2,
   'Item 2' = 3
};

HTML

<select data-ng-model="item" data-ng-options="v as k for (k, v) in itemlist"></select>

来源：https://stackoverflow.com/questions/19182961/ng-options-how-to-set-first-select-always-blank

标签

javascript

angularjs

options