HTML Forms and Validation events

1. Form Verification <form></form>

(1) Non-null verification (go blank)

(2) comparison verification (compared with a value)

(3) Scope validation (judging by a range)

(4) Fixed format verification: Telephone number, ID card number, mailbox, credit card number, etc., need to use regular expression to verify.

(5). Other validation

2. Regular expressions

Use symbols to describe writing rules:/ Middle Write Regular expression/

^: match at the beginning, $: match end;/^ve/with ve beginning/ve$/with VE end

\d: An arbitrary number

\w: An arbitrary number or letter

\s:

{n}: Repeat n-times the expression on the left

{M,n}: Repeat the expression on the left at least m times, up to N times
{m,}: Repeat at least M-times the expression on the left, at most

+: The expression on the left appears at least once, at most, equal to {1,}

*: The expression on the left appears at least 0 times, at most, equal to {0}

?: the expression on the left appears at least 0 times and appears at most 1 times, equivalent to {0,1}

[A,b,c]: Only one of the contents in square brackets can be taken

[A-z] or [1-9]: Take one of the ranges

|: delegate or; (): priority; \: Escaped--"\ (\)" This is the parenthesis that will appear, need to be escaped

3. Events

Events have three elements: event source, event data, event handler

Event bubbling: When an element is nested, an event is fired by the inner element, and the corresponding event of the external element is then triggered by default.

can add return false;

OnClick: mouse click Trigger

OnDblClick: Double-click Trigger

onMouseOver: Mouse movement above trigger

onMouseOut: Triggers when the mouse leaves

OnMouseMove: Triggers when the mouse moves above

onchange: Whenever content changes trigger

Onblur: triggers when losing focus

Onfocus: Triggers when focus is acquired

OnKeyDown: Trigger when button is pressed

OnKeyUp: Trigger When the button is lifted up

onkeypress: event occurs when the user presses and releases any alphanumeric keys. However, the system buttons (for example: arrow keys, function keys) cannot be identified.

Example: Verifying mailboxes based on regular expressions

123456789101112131415

function checkemail()  {       var v4 = trim(u4.value);       var reg = /^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$/;       if(v4.match(reg) != null)       {               imgs4.setAttribute("src","imges/1.png");               return true;       }       else       {              imgs4.setAttribute("src","imges/2.png");               return false;       }}

HTML Forms and Validation events