HTMLInputElement.stepUp() - Web APIs 编辑

The HTMLInputElement.stepUp() method increments the value of a numeric type of  <input> element by the value of the step attribute, or the default step value if the step attribute is not explicitly set. The method, when invoked, increments the value by (step * n), where n defaults to 1 if not specified, and step defaults to the default value for step if not specified.

The method, when invoked, changes the form control's value by the value given in the step attribute, multiplied by the parameter, within the constraints set on the form control. The default value for the parameter, if no value is passed, is 1. The method will not cause the value to exceed the set max value, or defy the constraints set by the step attribute.

If the value before invoking the stepUp() method is invalid—for example, if it doesn't match the constraints set by the step attribute—invoking the stepUp() method will return a value that does match the form controls constraints.

If the form control is non time, date, or numeric in nature, and therefore does not support the step attribute (see the list of supported input types in the table above), or if the step value is set to any, an InvalidStateError exception is thrown.

Syntax

element.stepUp( [ stepIncrement ] );

Parameters

stepIncrement

The optional  stepIncrement parameter is a numeric value.  If no parameter is passed, stepIncrement defaults to 1.

Example

Click the button in this example to increment the number input type:

HTML

<p>
  <label>Enter a number between 0 and 400 that is divisible by 5:
   <input type="number" step="5" id="theNumber" min="0" max="400">
  </label>
</p>
<p>
  <label>Enter how many values of step you would like to increment by or leave it blank:
   <input type="number" step="1" id="incrementer" min="0" max="25">
  </label>
</p>
<input type="button" value="Increment" id="theButton">

JavaScript

/* make the button call the function */
let button = document.getElementById('theButton')
button.addEventListener('click', function() {
  steponup()
})

function steponup() {
  let input = document.getElementById('theNumber')
  let val = document.getElementById('incrementer').value

  if (val) {  /* increment with a parameter */
    input.stepUp(val)
  } else {    /* or without a parameter. Try it with 0 */
    input.stepUp()
  }
}

CSS

input:invalid {
  border: red solid 3px;
}

Result

Note if you don't pass a parameter to the stepUp method, it defaults to 1. Any other value is a multiplier of the step attribute value, which in this case is 5. If you pass 4 as the stepIncrement, the input will stepUp by 4 * 5, or 20. If the parameter is 0, the number will not be incremented. The stepUp will not allow the input to out of range, in this case stopping when it reaches 400, and rounding down any floats that are passed as a parameter.

Try setting the step increment to 1.2. What happens when you invoke the method?

Try setting the value to 4, which is not valid. What happens when you invoke the method?

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• <input>
• HTMLInputElement
• HTMLInputElement.stepDown
• step, min and max attributes