how can i change the value of checkbox when i select a value from select input with js

问题

i want to learn that when i select a value from select input how can i change the value of checkbox.

<input type="checkbox" name="id" value="" id="mycheckbox1">

<select name="cat-1" id="myselectbox1">
    <option value="">Choose</option>      
    <option value="100">Value1</option>
    <option value="200">Value2</option>       
</select>

回答1:

Why would you want to?

Anyway:

window.addEventListener("load", function() { // on page load
  document.getElementById("myselectbox1").addEventListener("change", function() {
    document.getElementById("mycheckbox1").value = this.value;
  });
  document.getElementById("mycheckbox1").addEventListener("change", function() {
    console.log(this.value);
  });
});

<input type="checkbox" name="id" value="" id="mycheckbox1">

<select name="cat-1" id="myselectbox1">
  <option value="">Choose</option>
  <option value="100">Value1</option>
  <option value="200">Value2</option>
</select>

回答2:

function updateCheckbox() {
  var val = document.getElementById("myselectbox1").value;
  document.getElementById("mycheckbox1").checked = true;
  document.getElementById("mycheckbox1").value = val;
}

<input type="checkbox" name="id" value="" id="mycheckbox1">

<select onChange="updateCheckbox()" name="cat-1" id="myselectbox1">
  <option selected disabled>Choose</option>
  <option value="100">Value1</option>
  <option value="200">Value2</option>
</select>

回答3:

may i ask one more question

i changed my checkbox value if i have one more select input which id cat-2 how can i change name of cat-2 to chosen value of cat-1

For example; if i choose value1 ( its value=100) i want to change name of cat-2 to cat-100

```
<input type="checkbox" name="id" value="" id="mycheckbox1">

<select name="cat-1" id="myselectbox1">
<option value="">Choose</option>      
<option value="100">Value1</option>
<option value="200">Value2</option>       
</select>

<select name="cat-2" id="myselectbox2">
<option value="">Choose</option>      
<option value="300">Value3</option>
<option value="400">Value4</option>       
</select>

```

来源：https://stackoverflow.com/questions/62363989/how-can-i-change-the-value-of-checkbox-when-i-select-a-value-from-select-input-w

标签

javascript

jquery

select

checkbox