问题
I have 3 dropdown, the values filled dynamically with mysql. Now, I'm trying to cascade the 3 dropdown, but JS script is not working.
What I'm trying to do's:
Case 1: If the user choose a value from dropdown #1, the value of dropdown #2 depends on dropdown #1, the value of dropdown #3 depends on dropdown #2. E.g. State - City - Avenue
Case 2: The user can choose from 3 dropdown.
Case 3 and 4: If the user choose from dropdown #2, the values of dropdown #3 depends in dropdown #2 (but choosing a value in dropdown #3 is optional, if the dropdown #2 have already)
Form:
<form action='' method='post' id='loc'>
<select name="state" id="filter_region" class="state">
<option name="default" class="default" value="State" readonly>State</option>
<?php
foreach($result_state as $option){
if(isset($_POST['state']) && $_POST['state'] == $option->state)
echo '<option name="state" class="filter_by" selected value="'. $option->state .'">'. $option->state .'</option>';
else
echo '<option name="state" class="filter_by" value="'. $option->state .'">'. $option->state .'</option>';
};
?>
</select>
<select name="city" id="filter_city" class="city">
<option name="default" class="default" value="City" readonly>City</option>
<?php
foreach($result_city as $option){
if(isset($_POST['city']) && $_POST['city'] == $option->city)
echo '<option name="city" class="filter_by" selected value="'. $option->city .'">'. $option->city .'</option>';
else
echo '<option name="city" class="filter_by" value="'. $option->city .'">'. $option->city .'</option>';
};
?>
</select>
<select name="avenue" id="filter_mall" class="avenue">
<option name="default" class="default" value="Avenue" readonly>Avenue</option>
<?php
foreach($result_avenue as $option){
if(isset($_POST['avenue']) && $_POST['avenue'] == $option->avenue)
echo '<option name="avenue" class="default" selected value="'. $option->avenue .'">'. $option->avenue .'</option>';
else
echo '<option name="avenue" class="filter_by" value="'. $option->avenue .'">'. $option->avenue .'</option>';
};
?>
</select>
<input type="submit" value="submit" class="submit"/>
</form>
JS:
function cascadeSelect(parent, child){
var childOptions = child.find('option:not(.default)');
child.data('options',childOptions);
parent.change(function(){
childOptions.remove();
child
.append(child.data('options').filter('.filter_by' + this.value))
.change();
})
childOptions.not('.default, .filter_by' + parent.val()).remove();
}
$(function(){
cascadeForm = $('.loc');
state= cascadeForm.find('.state');
city= cascadeForm.find('.city');
avenue= cascadeForm.find('.avenue');
cascadeSelect(state, city);
cascadeSelect(city, avenue);
});
回答1:
I had created cascading parent-child select-boxes using AngularJS, but since you are using NativeJS, I tried to re-create using JS. The pre-requisite of my solution is a well-defined JSON based on which the select-boxes will be created. You'll have to create the JSON on server side or manually or wherever you are creating the select-box data. Below is the JSON format.:
Every select-box is a named object with following properties:
- Parent Attribute: Name of object which is the parent of this select-box object.
Options: Array of option objects, where each object contains: (a) Option Value (b) Parent Option Value - The parent select-box value with which the current value is mapped. (c) Option ID.
Selected Option: An object with two properties: (a) Currently selected value (b) ID of currently selected value.
Here is the working Plunker of the solution. Hope it helps.
----- EDIT: -----
On request of @User014019
Here is the another version of this drop-down solution where all the options in all select-boxes are visible initially, and parent-child relationships are set when user select a particular value.
Below is the code:
// reads the data and creates the DOM elements (select-boxes and their relevant options)
function initSelect(data) {
var select, option, input, filteredOptions;
for (var key in data) {
select = document.createElement("select");
select.name = key;
container.appendChild(select);
filteredOptions = optionFilter(data[key].availableOptions, data[data[key].parent], data[key]);
input = document.querySelector('select[name="' + key + '"');
input.setAttribute("onchange", "updateSelect(this)");
for (var i = 0; i < filteredOptions.length; i++) {
option = document.createElement("option");
option.value = filteredOptions[i].value;
option.innerHTML = filteredOptions[i].value;
input.appendChild(option);
}
input.options.selectedIndex = getSelectedIndex(filteredOptions, data[key]);
input.setAttribute('model', data[key].selectedOption.value);
}
}
// this function will be called on change of select-box
function updateSelect(element) {
var input, option;
setSelectedOption(element);
for (var key in data) {
filteredOptions = optionFilter(data[key].availableOptions, data[data[key].parent], data[key]);
input = document.querySelector('select[name="' + key + '"');
while (input.firstChild) {
input.removeChild(input.firstChild);
}
for (var i = 0; i < filteredOptions.length; i++) {
option = document.createElement("option");
option.value = filteredOptions[i].value;
option.innerHTML = filteredOptions[i].value;
input.appendChild(option);
}
input.options.selectedIndex = getSelectedIndex(filteredOptions, data[key]);
input.setAttribute('model', data[key].selectedOption.value);
}
}
// set the selected-option of select-box when it's changed
function setSelectedOption(element) {
var inputName = element.getAttribute("name");
var inputValue = getSelectedText(element);
var inputItem = data[inputName];
var selectedOption, filteredOptions;
// setting selected option of changed select-box
for (var i = 0; i < inputItem.availableOptions.length; i++) {
if (inputValue === inputItem.availableOptions[i].value) {
inputItem.selectedOption = inputItem.availableOptions[i];
break;
}
}
// setting child object selected option now
for (var key in data) {
if (data[key].parent === inputName) {
filteredOptions = optionFilter(data[key].availableOptions, data[data[key].parent], data[key]);
data[key].selectedOption = filteredOptions[0];
}
}
}
// get the text of select-box
function getSelectedText(element) {
if (element.selectedIndex == -1) {
return null;
}
return element.options[element.selectedIndex].text;
}
function getSelectedIndex(options, self) {
var index;
for (var i = 0; i < options.length; i++) {
if (self.selectedOption.value === options[i].value) {
index = i;
break;
}
}
return index;
}
// get filtered options based on parent's selected value
function optionFilter(items, parent, self) {
var result = [];
if (typeof parent !== "undefined") {
for (var i = 0; i < items.length; i++) {
if (typeof parent.selectedOption !== "undefined") {
if (parent.selectedOption !== null && items[i].parentValue === parent.selectedOption.value) {
result.push(items[i]);
}
}
}
if (typeof self.selectedOption === "undefined") {
self.selectedOption = null;
}
if (self.selectedOption === null) {
self.selectedOption = result[0];
}
return result;
} else {
return items;
}
}
来源：https://stackoverflow.com/questions/39009336/cascade-dropdown-using-js-not-working