<input type="number">

"number"类型的 <input> 元素用于让用户输入一个数字。其包括内置验证以拒绝非数字输入。浏览器可能会选择提供步进箭头，让用户可以使用鼠标增加和减少输入的值，或者只需用指尖敲击即可。

<input id="number" type="number">

值

A Number representing the value of the number entered into the input. You can set a default value for the input by including a number inside the value attribute, 像下面这样:

<input id="number" type="number" value="42">

使用 number 输入框

<input type="number"> elements can help simplify your work when building the user interface and logic for entering numbers into a form. When you create an number input with the proper type value, "number", you get automatic validation that the entered text is a number, and usually a set of up and down buttons to step the value up and down.

In addition, mobile browsers further help with the user experience by showing a special keyboard more suited for entering numbers when the user tries to enter a value. The following screenshot is taken from Firefox for Android:

一个简单的 number 输入框

In its most basic form, a number input can be implemented like this:

<label for="ticketNum">Number of tickets you would like to buy:</label>
<input id="ticketNum" type="number" name="ticketNum" value="0">

A number input is considered valid when empty and when a single number is entered, but is otherwise invalid. If the required attribute is used, the input is no longer considered valid when empty.

占位符

Sometimes it's helpful to offer an in-context hint as to what form the input data should take. This can be especially important if the page design doesn't offer descriptive labels for each <input>. This is where placeholders come in. A placeholder is a value that demonstrates the for the value should take by presenting an example of a valid value, which is displayed inside the edit box when the element's value is "". Once data is entered into the box, the placeholder disappears; if the box is emptied, the placeholder reappears.

Here, we have an "number" input with the placeholder "Multiple of 10". Note how the placeholder disappears and reappears as you manipulate the contents of the edit field.

<input type="number" placeholder="Multiple of 10">

控制步进尺寸

By default, the up and down buttons provided for you to step the number up and down will step the value up and down by 1. You can change this by providing a step attribute, which takes as its value a number specifying the step amount. Our above example contains a placeholder saying that the value should be a multiple of 10, so it makes sense to add a step value of 10:

<input type="number" placeholder="multiple of 10" step="10">

In this example you should find that the up and down step arrows will increase and decrease the value by 10 each time, not 1. You can still manually enter a number that's not a multiple of 10, but it will be considered invalid.

指定 最小&最大 值

You can use the min and max attributes to specify a minimum and maximum value that the field can have. For example, let's give our example a minimum of 0, and a maximum of 100:

<input type="number" placeholder="multiple of 10" step="10" min="0" max="100">

In this updated version, you should find that the up and down step buttons will not allow you to go below 0 or above 100. You can still manually enter a number outside these bounds, but it will be considered invalid.

允许 小数值

One issue with number inputs is that their step size is 1 by default — if you try to enter a number with a decimal, such as "1.0", it will be considered invalid. If you want to enter a value that requires decimals, you'll need to reflect this in the step value (e.g. step="0.01" to allow decimals to two decimal places). Here's a simple example:

<input type="number" placeholder="1.0" step="0.01" min="0" max="10">

See that this example allows any value between 0.0 and 10.0, with decimals to two places. "9.52" is valid, but "9.521" is not, for example.

控制 input 尺寸

<input> elements of type "number" don't support form sizing attributes such as size. You'll have to resort to CSS to change the size of these controls.

For example, to adjust the width of the input to be only as wide as is needed to enter a three-digit number, we can change our HTML to include an ID and to shorten our placeholder since the field will be too narrow for the text we have been using so far:

<input type="number" placeholder="x10" step="10" min="0" max="100" id="number">

Then we add some CSS to narrow the width of the element with the ID "number":

#number {
  width: 3em;
}

The result looks like this:

提供建议值

You can provide a list of default options from which the user can select by specifying the list attribute, which contains as its value the ID of a <datalist>, which in turn contains one <option> element per suggested value; each option's value is the corresponding suggested value for the number entry box.

<input id="ticketNum" type="number" name="ticketNum" list="defaultNumbers">
<span class="validity"></span>
<datalist id="defaultNumbers">
  <option value="10045678">
  <option value="103421">
  <option value="11111111">
  <option value="12345678">
  <option value="12999922">
</datalist>

验证

We have alread mentioned a number of validation features of number inputs, but let's review them now:

• <input type="number"> elements automatically invalidate any entry that isn't a number (or empty, unless required is specified).
• You can use the required attribute to make an empty entry invalid, i.e. the input has to be filled in.
• You can use the step attribute to constrain valid values to a certain set of steps (e.g. multiples of 10).
• You can use the min and max attributes to constrain valid values to lower and upper bounds.

The following example exhibits all of the above features, as well as using some CSS to display valid and invalid icons when the input value is valid/invalid:

<form>
  <div>
    <label for="balloons">Number of balloons to order (multiples of 10):</label>
    <input id="balloons" type="number" name="balloons" step="10" min="0" max="100" required>
    <span class="validity"></span>
  </div>
  <div>
    <input type="submit">
  </div>
</form>

Try submitting the form with different invalid values entered — e.g. no value, a value below 0 or above 100, a value that is not a multiple of 10, or a non-numerical value — and see how the error messages the browser gives you differ with different ones.

The CSS applied to this example is as follows:

div {
  margin-bottom: 10px;
}
input:invalid+span:after {
  content: '✖';
  padding-left: 5px;
}
input:valid+span:after {
  content: '✓';
  padding-left: 5px;
}

Here we use the :invalid and :valid pseudo classes to display an appropriate invalid or valid icon as generated content on the adjacent <span> element, indicating if the current value is valid. We put it on a separate <span> element for added flexibility; some browsers don't display generated content very effectively on some types of form inputs (read for example the section on <input type="date"> validation).

验证模式

<input type="number"> elements do not support use of the pattern attribute for making entered values conform to a specific regex pattern. The rationale for this is that number inputs can't contain anything except numbers, and you can constrain the minimum and maximum number of valid digits using the min and max attributes, as explained above.

范例

We've already covered the fact that by default, the increment is 1, and you can use the step attribute to allow decimal inputs. Let's take a closer look. In the following example we've set up a form for entering the user's height; it defaults to accepting a height in meters, but you can click the relevant button to change the form to accept feet and inches instead. The input for the height in meters accepts decimals to two places.

The HTML looks like this:

<form>
    <div class="metersInputGroup">
        <label for="meters">Enter your height — meters:</label>
        <input id="meters" type="number" name="meters" step="0.01" min="0" placeholder="e.g. 1.78" required>
        <span class="validity"></span>
    </div>
    <div class="feetInputGroup" style="display: none;">
        <span>Enter your height — </span>
        <label for="feet">feet:</label>
        <input id="feet" type="number" name="feet" min="0" step="1">
        <span class="validity"></span>
        <label for="inches">inches:</label>
        <input id="inches" type="number" name="inches" min="0" max="11" step="1">
        <span class="validity"></span>
    </div>
    <div>
      <input type="button" class="meters" value="Enter height in feet and inches">
    </div>
    <div>
        <input type="submit" value="Submit form">
    </div>
</form>

You'll see that we are using many of the attributes we've already looked at in the article earlier on. Since we want to accept a meter value in centimeters, we've set the step value to 0.01, so that values like 1.78 are not seen as invalid. We've also provided a placeholder for that input.

We've hidden the feet and inches inputs initially using style="display: none;" so that meters is the default entry type.

Now on to the CSS — this looks very similar to the validation styling we saw before; nothing remarkable here:

div {
  margin-bottom: 10px;
  position: relative;
}
input[type="number"] {
  width: 100px;
}
input + span {
  padding-right: 30px;
}
input:invalid+span:after {
  position: absolute;
  content: '✖';
  padding-left: 5px;
}
input:valid+span:after {
  position: absolute;
  content: '✓';
  padding-left: 5px;
}

And finally, the JavaScript:

var metersInputGroup = document.querySelector('.metersInputGroup');
var feetInputGroup = document.querySelector('.feetInputGroup');
var metersInput = document.querySelector('#meters');
var feetInput = document.querySelector('#feet');
var inchesInput = document.querySelector('#inches');
var switchBtn = document.querySelector('input[type="button"]');
switchBtn.addEventListener('click', function() {
  if(switchBtn.getAttribute('class') === 'meters') {
    switchBtn.setAttribute('class', 'feet');
    switchBtn.value = 'Enter height in meters';
    metersInputGroup.style.display = 'none';
    feetInputGroup.style.display = 'block';
    feetInput.setAttribute('required', '');
    inchesInput.setAttribute('required', '');
    metersInput.removeAttribute('required');
    metersInput.value = '';
  } else {
    switchBtn.setAttribute('class', 'meters');
    switchBtn.value = 'Enter height in feet and inches';
    metersInputGroup.style.display = 'block';
    feetInputGroup.style.display = 'none';
    feetInput.removeAttribute('required');
    inchesInput.removeAttribute('required');
    metersInput.setAttribute('required', '');
    feetInput.value = '';
    inchesInput.value = '';
  }
});

After declaring a few variables, we add an event listener to the button to control the switching mechanism. This is pretty simple, mostly involving changing over the button class and label, and updating the display values of the two sets of inputs when the button is pressed. Note that we're not converting back and forth between meters and feet/inches here, which a real-life web application would probably do.

规范

浏览器兼容性

相关链接

• HTML forms guide
• <input>
• <input type="tel">