To set the default value of the HTML input box, the value attribute is mainly used. The specific methods are as follows: 1. Add a value attribute in the <input> tag, such as <input type="text" name="username" value="JohnDoe">, and the default value will be displayed when the page is loaded; 2. Distinguish between value and placeholder, the former is the actual default value, and the latter is only the prompt text; 3. The default value can be dynamically modified through JavaScript, such as using document.querySelector("input[name='username']").value = "NewDefault"; to implement update operations in interactive logic.
Sure, here's how to set a default value for an HTML input field — it's pretty straightforward and commonly used when you want to pre-fill forms or provide placeholder suggestions.

Use the value
Attribute
The most direct way is using the value
attribute inside your <input>
tag. Whatever you put in there will show up as the initial content of the input box.

For example:
<input type="text" name="username" value="JohnDoe">
This shows "JohnDoe" already filled in the input field when the page loads.

You can use this with different input types like numbers, emails, or even hidden fields.
Consider Using placeholder
(But It's Not the Same)
A lot of people confuse placeholder
with a default value, but they're not the same thing. The placeholder
text disappears as soon as the user starts typing, while the value
stays until changed.
Use placeholder
if you're giving a hint rather than setting a real default:
<input type="text" name="email" placeholder="example@example.com">
So keep in mind:
- Use
value
for actual defaults - Use
placeholder
only for temporary hints
Resetting or Updating Default Values ??with JavaScript
If you need to dynamically change the default value based on user actions or other conditions, you can do that with JavaScript.
Here's a quick example:
document.querySelector("input[name='username']").value = "NewDefault";
This might be useful if you have form steps or conditional logic where inputs should change based on selections.
Just remember: once you set a value with JavaScript, it behaves just like a regular default — unless the user changes it, that value will stay.
Wrapping Up
Setting a default value in an HTML input field mostly comes down to the value
attribute. You can enhance or modify it later with JavaScript if needed, and don't mix it up with placeholder
.
That's basically it — simple, but useful in a lot of forms.
The above is the detailed content of How to set a default value for an HTML input field?. For more information, please follow other related articles on the PHP Chinese website!

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