HTMLInputElement: stepDown() method
The
HTMLInputElement.stepDown([n])
method decrements the
value of a numeric type of <input>
element by the value of the
step
attribute or up
to n
multiples of the step attribute if a number is passed as the
parameter.
The method, when invoked, decrements 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.
Valid on all numeric, date, and time input types that support the step attribute, including date, month, week, time, datetime-local, number, and range.
Given <input id="myTime" type="time" max="17:00" step="900" value="17:00">
,
invoking myTime.stepDown(3)
will change the value to 16:15, decrementing the
time by 3 * 900
, or 45 minutes. myTime.stepDown()
, with no
parameter, would have resulted in 16:45
, as n
defaults to
1
.
html
<!-- decrements by intervals of 900 seconds (15 minute) -->
<input type="time" max="17:00" step="900" />
<!-- decrements by intervals of 7 days (one week) -->
<input type="date" max="2019-12-25" step="7" />
<!-- decrements by intervals of 12 months (one year) -->
<input type="month" max="2019-12" step="12" />
However, calling stepDown
on <input type="time" max="17:00" step="900">
would not set the value to 17:00
, as one would expect — and as it does for stepUp
when the input is <input type="time" min="17:00" step="900">
. Instead, the first call to stepDown
will set the initial value to 23:45
even though the max
attribute is set. The second call will set the value to 17:00
. And the third call to will set the value to 16:45
.
js
let input1 = document.createElement("input");
input1.setAttribute("type", "time");
input1.setAttribute("min", "17:00");
input1.setAttribute("step", 900);
console.log(input1.value); // ""
input1.stepUp();
console.log(input1.value); // "17:00"
// However
let input2 = document.createElement("input");
input2.setAttribute("type", "time");
input2.setAttribute("max", "17:00");
input2.setAttribute("step", 900);
console.log(input2.value); // ""
input2.stepDown();
console.log(input2.value); // "23:45"
input2.stepDown();
console.log(input2.value); // "17:00"
input2.stepDown();
console.log(input2.value); // "16:45"
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
within the form control. The default value for the parameter, if not is passed, is 1.
The method will not cause the value to go below the
min
value set or defy the
constraints set by the
step
attribute. A
negative value for n
will increment the value, but will not increment
beyond the max
value.
If the value before invoking the stepDown()
method is invalid, for
example, if it doesn't match the constraints set by the step
attribute,
invoking the stepDown()
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 above), or if the step
value is set to any
, an
InvalidStateError
exception is thrown.
HTMLInputElement.stepDown()
-
Decrements the
value
by (step
* n), where n defaults to 1 if not specified. Throws anInvalidStateError
exception:
Syntax
js
stepDown()
stepDown(stepDecrement)
Parameters
stepDecrement
Optional-
A numeric value. If no parameter is passed, stepDecrement defaults to 1.
If the value is a float, the value will decrement as if
Math.floor(stepDecrement)
was passed. If the value is negative, the value will be incremented instead of decremented.
Return value
None (undefined
).
Examples
Click the button in this example to decrement the number input type:
HTML
html
<p>
<label for="theNumber">
Enter a number between 0 and 400 that is divisible by 5:
</label>
<input type="number" step="5" id="theNumber" min="0" max="400" />
</p>
<p>
<label for="decrementButton">
Enter how many values of step you would like to decrement by or leave it
blank:
</label>
<input type="number" step="1" id="decrementInput" min="-2" max="15" />
</p>
<input type="button" value="Decrement" id="theButton" />
JavaScript
js
/* make the button call the function */
let button = document.getElementById("theButton");
button.addEventListener("click", () => {
stepOnDown();
});
function stepOnDown() {
let input = document.getElementById("theNumber");
let val = document.getElementById("decrementInput").value;
if (val) {
// decrement with a parameter
input.stepDown(val);
} else {
// or without a parameter. Try it with 0, 5, -2, etc.
input.stepDown();
}
}
CSS
css
input:invalid {
border: red solid 3px;
}
Result
Note if you don't pass a parameter to the stepDown()
method, it defaults
to 1. Any other value is a multiplier of the step
attribute value, which in
this case is 5. If we pass 4
as the stepDecrement
, the input will stepDown
by
4 * 5
, or 20
. If the parameter is 0
, the number will not be
decremented. The stepDown()
method will not allow the input to go out of range, in this
case stopping when it reaches 0 and rounding down and floats that are passed as a
parameter.
Try setting the step decrement input to 1.2
. What happens when you invoke the
method?
Try setting the value to 44
, which is not valid. What happens when you
invoke the method?
Specifications
Specification |
---|
HTML Standard # dom-input-stepdown-dev |
Browser compatibility
BCD tables only load in the browser
See also
<input>
HTMLInputElement
HTMLInputElement.stepUp()
-
step
,min
andmax
attributes