What is the difference between readonly true readonly readonly

Question

What is the difference between     lt input name  TextBox1  type  text  id  TextBox1  readonly  true    gt    and    lt input name  TextBox1  type  text  id  TextBox1  readonly  readonly    gt    When i set readonly to true it works somewhat different from readonly  readonly   W3C standard says readonly should be  readonly   amp  not  true   Why most of the browsers allow readonly  true  which has somewhat different functionality than readonly  readonly

User · Answer

readonly  readonly  is xhtml syntax  In xhtml boolean attributes are written this way  In xhtml  attribute minimization    lt input type  checkbox  checked gt   isn t allowed  so this is the valid way to include boolean attributes in xhtml  See this page for more information    If your document type is xhtml transitional or strict and you want to validate it  use readonly  readonly otherwise readonly is sufficient

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readonly  quot true quot  is invalid HTML5  readonly  quot readonly quot  is valid  HTML5 spec  http   www w3 org TR html5 forms html attr-input-readonly    The readonly attribute is a boolean attribute  http   www w3 org TR html5 infrastructure html boolean-attributes    The presence of a boolean attribute on an element represents the true value  and the absence of the attribute represents the false value  If the attribute is present  its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute s canonical name  with no leading or trailing whitespace   Conclusion  The following are valid  equivalent and true   lt input type  quot text quot  readonly   gt   lt input type  quot text quot  readonly  quot  quot    gt   lt input type  quot text quot  readonly  quot readonly quot    gt   lt input type  quot text quot  readonly  quot ReAdOnLy quot    gt   The following are invalid   lt input type  quot text quot  readonly  quot 0 quot    gt   lt input type  quot text quot  readonly  quot 1 quot    gt   lt input type  quot text quot  readonly  quot false quot    gt   lt input type  quot text quot  readonly  quot true quot    gt   The absence of the attribute is the only valid syntax for false   lt input type  quot text quot   gt   Recommendation If you care about writing valid XHTML  use readonly  quot readonly quot   since  lt input readonly gt  is invalid and other alternatives are less readable  Else  just use  lt input readonly gt  as it is shorter

User · Answer

This is a property setting rather than a valued attribute  These property settings are values per see and don t need any assignments to them  When they are present  an element has this boolean property set to true  when they re absent they re false    lt input type  text  readonly   gt    It s actually browsers that are liberal toward value assignment to them  If you assign any value to them it will simply get ignored  Browsers will only see the presence of a particular property and ignore the value you re trying to assign to them   This is of course good  because some frameworks don t have the ability to add such properties without providing their value along with them  Asp net MVC Html helpers are one of them  jQuery used to be the same until version 1 6 where they added the concept of properties   There are of course some implications that are related to XHTML as well  because attributes in XML need values in order to be well formed  But that s a different story  Hence browsers have to ignore value assignments   Anyway  Never mind the value you re assigning to them as long as the name is correctly spelled so it will be detected by browsers  But for readability and maintainability it s better to assign meaningful values to them like   readonly  true   lt -- arguably best human readable readonly  readonly    as opposed to  readonly  johndoe  readonly  01 01 2000    that may confuse future developers maintaining your code and may interfere with future specification that may define more strict rules to such property settings

User · Answer

Giving an element the attribute readonly will give that element the readonly status  It doesn t matter what value you put after it or if you put any value after it  it will still see it as readonly  Putting readonly  false  won t work   Suggested is to use the W3C standard  which is readonly  readonly

User · Answer

I m not sure how they re functionally different  My current batch of OS X browsers don t show any difference   I would assume they are all functionally the same due to legacy HTML attribute handling  Back in the day  any flag  Boolean  attribute need only be present  sans value  eg   lt input readonly gt   lt option selected gt    When XHTML came along  this syntax wasn t valid and values were required  Whilst the W3 specified using the attribute name as the value  I m guessing most browser vendors decided to simply check for attribute existence

User · Answer

According to HTML standards  the use of   lt input name  TextBox1  type  text  id  TextBox1  readonly  gt    is enough to make the input element readonly  But  XHTML standard says that the usage listed above is invalid due to attribute minimization  You can refer to the links below   https   www w3 org TR xhtml1 diffs html h-4 5  http   www w3schools com tags att input readonly asp

[html] What is the difference between readonly="true" & readonly="readonly"?

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