html-forms

HTML form uses the form element

• action attribute determines how the information will be processed
  Forms have an input box using input which user can input text, radio button or submit

<form>  <input type="text">  </form>

To match a label to an input, the for attribute of a label must match the id of the input

<label for="email">Email</label> <!-- for="email" -->
<input type="email" name="email" id="email"> <!-- id="email"-->

When it’s matched, when clicking the corresponding label, the input will be highlighted.

Forms contains a submit button, when a user presses enter, that button is clicked and all the form is submitted.

<button type="submit">Submit</button>

• for a form to be submit button, the type="submit" is included as an attribute

Type
The complete type of input can be found https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#input_types
Here are the commonly used input types
Email - validate real email before submitting

Number - only numbers can be entered, like tel, on some devices a numeric keyboard appear

Password - the text content is obscured, also bring up the password manager

Datetime-local - browser will display and date-time selector

File - show and file picker menu
Reset - a button that clear all the information of the form to default value
Radio - select only one button in a fieldset

  <fieldset>
    <legend>Choose one</legend>
    <input id="one" type="radio" name="choose">
    <label for="one">One</label><br>
    <input id="two" type="radio" name="choose">
    <label for="two">Two</label>
  </fieldset>

• All the options are enclosed with fieldset, the title of selection is defined by legend
• all the options in the fieldset must have matching name so a unique choice can be selected
  
  Checkbox - similar to radio but type=radio, can select multiple

Dropdown list - select one or more from a list of items

<select id="choose" name="choose">  
  <option value="one">One</option>  
  <option value="two">Two</option>   
</select>

• when the select has attribute multple, multiple items can be selected via Ctrl
• select can also have the attribute size which determine how many items to show in that dropdown list

Datalist - text input box with a list of pre-defined options to choose.

  <input list="browsers" name="browser">
  <datalist id="browsers">
    <option value="Edge">
</datalist>

• datalist uses list and id for matching

Input Attributes
Full list is https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#attributes
Here are some common ones

Placeholder

<input placeholder="12345 St" type="name" name="" id="address">

Using the placeholder attribute, the form will have suggested text when the user enters anything, the placeholder text will disappear.

Value

<input value="12345 St" type="name" name="" id="address">

The value attribute will pre-populate the field for an user rather than giving suggestions.

Size

<input size="20">

Changes how long the input field is.

Minmax/step

<input min="123" max="1980-12-11" maxlength="10" step="3">

• min max defines the range of value that can be input (can also be date, week etc.)
• maxlength defines the number of characters in a box
• step is intervals allowed, in this case only multiple of 3 are okay

Pattern
regular expression code that validate against a input

Required

<input type="text" required>

Checked
When the page load, the checkbox or radio will be checked by default

Autofocus
When the page load, the focus goes to that input box.

Form Attributes
Autocomplete

<form action="" autocomplete="on"></form>

With autocomplete on, the form will autofill based on what the user entered before.

Readonly

<input readonly value="can't change">

The input will have the pre-defined value and can’t be changed.

Disabled

Similar to readonly, but also makes it unclickable.