github.com/fjuedes/utl_html
This go package defines a type T_HTML, with functions/methods to build an HTML document from the ground up. For the most used HTML-tags there is a corresponding function/method with the same name, just with the first letter capitalized. The Div() function/method for example generates complete
$Id: UTL_HTML.go 79 2025-04-29 20:33:24Z fjuedes $
func HelloWorld() {
FileName := "Test_HelloWorld.html"
// Generates:
v_Doc := New(GC_DocTypeHTML5). // <!DOCTYPE html>
HtmlOpen(). // <html>
HeadOpen(). // <head>
Title("Hello World in HTML"). // <title>Hellow World in HTML</title>
TagCloseTop(). // </head>
BodyOpen(). // <body>
POpen().I("Hello ").B("World!"). // <p><i>Hello</i> <b>World!</b></p>
TagCloseAll() // </body></html>
if e := os.WriteFile(FileName,[]byte(v_Doc.String()),0644); e != nil {
panic(e.Error())
} else {
fmt.Printf("***** VERIFY file »%s« in a browser.\n",FileName)
} // END if
} // END HelloWorld
Please find a thematically ordered list of the exported functions and methods of the T_HTML object below. Usually the name of the function/method is the name of the HTML-element, just with the first letter capitalized, for example the tag is created through the method Title(). Some tags will never be generated with their complete content, for example the <body> tag. So there is no Body() method defined, but a BodyOpen() method which generates the opening tag only. These tags are tracked in an internal tag-stack and will be closed semi-automagically when one of the TagClose...() methods is called.
Funtions whose name end with the letter "f" work similar to fmt.Printf, accepting a string as a format-mask and a variable number of data-items of any type. For example the B(string) method encapsulates content in <b> tags: <b>bold text</b>. The simliar named method Bf(string, any...) method formats data-items according to the format-mask and encapsulates the resulting string into the <b> tag. Example: Bf("Parametervalue is '%d'.",p_Value) will append <b>Parametervalue is '4711'.</b> to the HTML document if the value of p_Value is the number 4711.
Some functions have been also implemented to return the generated tags as strings which sometimes this is a useful hack…
The list below contains the basic functions to handle the T_HTML struct: Creation of a new document-variable, appending strings and NewLine, the Stringer interface and write functions.
The list below contains generic functions to build tags for any MarkUp language: From building complete tags with or without content, with or without attributes to opening and closing tags. By using these functions any type of MarkUp language document can be built.
func Test_XML(t *testing.T) {
FileName := "Test_XML.svg"
v_Doc := New(GC_DocTypeNONE).
AppendString(`<?xml version="1.0" encoding="UTF-8" standalone="no"?>`).NL().
AppendString(`<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">`).NL().
TagOpen("svg","width","512", "height","512", "viewBox","-70.5 -70.5 391 391", "xmlns","http://www.w3.org/2000/svg", "xmlns:xlink","http://www.w3.org/1999/xlink").
Tag("rect","","fill","#fff","stroke","#000","x","-70","y","-70","width","390","height","390").
TagOpen("g","opacity","0.8").
Tag("rect","","x","25","y","25","width","200","height","200","fill","lime","stroke-width","4","stroke","magenta").
Tag("circle","","cx","125","cy","125","r","75","fill","orange").
Tag("polyline","","points","50,150 50,200 200,200 200,100","stroke","red","stroke-width","4","fill","none").
Tag("line","", "x1","50", "y1","50" ,"x2","200" ,"y2","200", "stroke","blue", "stroke-width","4").
TagCloseAll()
if e := os.WriteFile(FileName,[]byte(v_Doc.String()),0644); e != nil {
t.Errorf(e.Error())
} else {
fmt.Printf("***** VERIFY file »%s« in a browser.\n",FileName)
} // END if
} // END Test_HelloWorld
Valid HTML documents must contain at least three tags: The tag encloses the entire document. The tag contains information about the text written in the body. The tag contains the information that is displayed by the browser.
The document header contains (meta-)information about the HTML-document, defined using the tags , , , and <title>. - And yes, the <script> tag can still be used in HTML-document headers, but that's so 1990's… just don't do this anymore!
The list below contains basic tags to structure the document-content: Headers, line breaks, horizontal rulers, paragraphs, divisions and inline-containers.
Below list contains direct formatting HTML tags in all four flavors, for example: B() and Bf() for the T_HTML Type and B() and Bf() returning a string. The use of these »ancient« formatting tags is controversial as formatting with CSS is more flexible and separates the data (HTML) from the presentation (CSS).
🚧 Currently under construction 🚧 TODO: More functions for other input-types
🚧 Currently under construction 🚧 TODO: more functions for complex data-types
Methods to support the creation of HTML-Tables, starting with static tables to the generation of header- and data-rows from structures, maps and slices.
Example for a simple static table:
v_Doc := New(GC_DocTypeHTML5).
HtmlOpen().
HeadOpen("id","4711").
Base("/test/","_self").
Meta("http-equiv","content-type","content","text/html; charset=UTF-8").
Meta("name","viewport", "content","width=device-width, initial-scale=0.9").
Link("stylesheet","text/css","static/Default.css").
Link("stylesheet","text/css","static/Bookmarks.css").
Title("TableTest").
TagCloseUntil("head").
BodyOpen().
TableOpen("class","class4table").
Captionf("class4caption","Static Table Test performed at %s.",time.Now().Format("2006-01-02T15:04:05")).
TheadOpen().
TrTh("class4tr","class4th","Name","Age","City","Occupation").
TagCloseTop(). // thead
TbodyOpen().
TrTd("class4tr","class4td","Alice","28","Old York","Software Engineer").
TrTd("class4tr","class4td","Bob","42","Lost Angeles","Data Scientist").
TrTd("class4tr","class4td","Charlie","61","Charleston","Freelancer").
TagCloseAll()
fmt.Println(v_Doc)
The variable v_Doc contains the whole HTML document, which can be extracted as a string and, printed to an http.ResponseWriter for example.
Beyond just simple static tables there is a group of methods implemented that handle structs, maps and slices. The methods TrThStruct() and TrTdStruct() generate header- and data rows from structures. For example we have a simplified structure for stock symbols (i will explain the html struct-tags later):
type t_TickerSymbol struct {
Name string `html:"ColHeader='Full Name' HeaderClass='AdditionalHeaderClass'"`
Type string `html:"DataClass='AdditionalDataClass'"`
LastPrice float32 `html:"Style='text-align: right; color: green;'"`
LastVolume int `html:"Style='text-align: right; color: blue;'"`
} // END t_TickerSymbol
To generate the table-header row the following snippet can be used:
TableOpen("class","class4table").
Captionf("class4caption",Caption,time.Now().Format("2006-01-02T15:04:05")).
TheadOpen().
TrThStruct("class4tr","class4th","Symbol",t_TickerSymbol{}).
TagCloseTop().
…
The method TrThStruct() takes CSS class-names for the and the tag, one additional column-name (we see later for what that is being used) and an empty t_TickerSymbol to generate a … structure. No loop necessary!
Data-rows are handled by the method TrTDStruct(), for example:
…
TbodyOpen().
TrTdStruct("class4tr","class4td","YHOO",MyTickerSymbol).
…
However that does not make much sense, as this takes care of only a single row of data. You will rarely use the TrTdStruct method directly, but it is used by the methods that handle entire maps and slices. If we have the following data:
var TickerTable = map[string]t_TickerSymbol{
"XOMO" : {Name: "YieldMax XOM Option Income Strategy ETF", Type: "ETF", LastPrice: 14.48, LastVolume: 46165},
"EURUSD": {Name: "Euro US Dollar", Type: "Currency", LastPrice: 1.0813},
"TB91D" : {Name: "91 Day Treasury Bill", Type: "FixedIncome", LastPrice: 4.1900},
"GSHRU" : {Name: "Gesher Acquisition Corp. II", Type: "IPO", LastPrice: 10.02, LastVolume: 6324701},
"EACAX" : {Name: "Eaton Vance California Municipal Opportunities Fund Class A", Type: "Mutual Fund", LastPrice: 10.99},
"CNP" : {Name: "CenterPoint Energy, Inc (Holding Co) Common Stock", Type: "Stock", LastPrice: 35.77, LastVolume: 8615303},
"SPX" : {Name: "S&P 500", Type: "Index", LastPrice: 5667.5600},
}
The whole ticker-table can be generated with this code:
…
TableOpen("class","class4table").
Captionf("class4caption",Caption,time.Now().Format("2006-01-02T15:04:05")).
TheadOpen().
TrThStruct("class4tr","class4th","Symbol",t_TickerSymbol{}).
TagCloseTop().
TbodyOpen().
TrTdMap("class4tr","class4td",CmpAsc,TickerTable).
…
See the full example in the file UTL_HTML_test as func Test_Table_MapStrStruct(t *testing.T).
The method TrThStruct accepts any struct-type and non-exported fields of the struct{} are skipped.
The method TrTdStruct accepts any struct-type and non-exported fields of the struct{} are skipped. Pointer fields are dereferenced and nil-values are replaced with " "
The method TrTdMap loops through all the keys of the map - sorted or unsorted - and generates the data-rows. This method can process the following types of maps:
Keys and values are being converted into strings using fmt.Sprint, composite types will therefore be converted into strings according to their Stringer interface which might not be the desired result.
In a very similar way, the method TrTdSlice() is processes slices into table data-rows. The following slice-types are supported:
Again, values are being converted into strings using fmt.Sprint, so composite types will be converted into strings according to their Stringer interface.
Now finally, about the struct-tags in the example t_TickerSymbol structure: When you create your own data-structures, you can add additional information to each field of your structure to control how HTML is generated. The syntax of the html struct-tag:
html:"Skip" - Skip this fieldhtml:"ColHeader='HeaderText'" - Use 'Headertext' instead of field-namehtml:"HeaderClass='CSS class-name'" - add class-name to taghtml:"DataClass='CSS class-name'" - add class-name to taghtml:"Style="CSS Declaration" - add style attribute to or tagAll combinations are supported, for example:
html:"ColHeader='PrimaryKey'" HeaderClass='Centered' DataClass='Centered' Style='color: red;'
The keywords "ColHeader", "HeaderClass", "DataClass", "Skip" and "Style" are case insensitive, the tag-name "html" is case-sensitive.
Please use the html struct-tag only as last resort: Remember the the »Separation of Concerns«:
Embedding style information into the HTML code violates this design philosophy!
Usually data is stored in some back-end systems like relationbal Databases, organized in tables. UTL_HTML directly supports SQL rowsets; the following table is defined in the attached SQLite database:
CREATE TABLE "DuckBreeds" (
"Breed" TEXT NOT NULL,
"EggColor" TEXT NOT NULL,
"EggSize" TEXT NOT NULL,
"EggProduction" TEXT NOT NULL,
"Class" TEXT NOT NULL,
"WeightRange" TEXT NOT NULL,
"Mothering" TEXT NOT NULL,
"Foraging" TEXT NOT NULL,
"Hardiness" TEXT NOT NULL,
"Personality" TEXT NOT NULL,
"Flying" INTEGER NOT NULL,
CONSTRAINT "pk_DuckBreeds" PRIMARY KEY("Breed")
);
Only a few lines of code are necessary to display the content of this table as an HTM document:
// Open Database
dbh,err := sql.Open("sqlite","Ducks.sqlite3")
if err != nil { panic(err) }
defer dbh.Close()
// Perform SQL-Query
Rows,err := dbh.Query("SELECT * FROM DuckBreeds ORDER BY 1")
if err != nil { panic(err) }
defer Rows.Close()
// Generate HTML-Table
v_Doc := New(GC_DocTypeHTML5).
HtmlOpen().
HeadOpen("id","0815").
Base("/test/","_self").
Meta("http-equiv","content-type","content","text/html; charset=UTF-8").
Meta("name","viewport", "content","width=device-width, initial-scale=0.9").
Link("stylesheet","text/css","static/Default.css").
Link("stylesheet","text/css","static/Bookmarks.css").
Title("TableTest").
TagCloseUntil("head").
BodyOpen().
TableOpen("class","class4table").
Captionf("class4caption",Caption,time.Now().Format("2006-01-02T15:04:05")).
TheadOpen().
TrThSqlRows("class4tr","class4th",Rows).
TagCloseTop().
TbodyOpen().
TrTdSqlRows("class4tr","class4td",Rows).
TagCloseAll()
The methods TrTHSqlRows and TrTdSqlRows retrieve the column-headers and the data-rows from the result-set of the query and generate the column-headers and the data-rows.
For more examples see the files: »UTL_HTML_*test.go«
The code snippet below generates an HTML form with an additional field when the username is "admin"
...
BMAppHeader().
BodyOpen("id","ToP").
FormOpen("formaction",http.MethodPost,"class","FormArea").
TableOpen("class","FormTable").
Captionf("FormTableCaption","Add new Bookmar/Folder in %s",v_Parent.NamePath).
HiddenField("p_FormName","AddForm").
HiddenField("p_ParentID",strconv.Itoa(v_Parent.ObjectID)).
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("Name","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.TextField("p_Name","50","150","","class","FormTextField"),"class","FormTableCell").
TagCloseUntil("tr").
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("Description","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.TextField("p_Description","50","1000","","class","FormTextField"),"class","FormTableCell").
TagCloseUntil("tr").
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("URL","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.TextField("p_URL","50","1000","","class","FormTextField"),"class","FormTableCell").
TagCloseUntil("tr").
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("Keywords","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.TextField("p_Keywords","50","1000","","class","FormTextField"),"class","FormTableCell").
TagCloseUntil("tr").
WHEN(User == BMAppDB.GC_UserAdmin). // admin can change ownership, so add the Owner field to the form
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("Owner","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.TextField("p_Owner","50","100",User,"class","FormTextField"),"class","FormTableCell").
TagCloseUntil("tr").
ENDWHEN().
TrOpen("class","FormTableRow").
Td(UTL_HTML.Span("Public","FormPromptField"),"class","FormTableCell").
Td(UTL_HTML.BoolField("p_Public",true,"class","FormBoolField"),"class","FormTableCell").
TagCloseUntil("tr").
TrOpen("class","FormTableButtonRow").
TdOpen("class","FormTableButtonCell","colspan","2").
SubmitButton("p_Submit", "Cancel", "Cancel", "class","FormSubmitButton").
SubmitButton("p_Submit", "Save", "Save", "class","FormSubmitButton").
CloseTagsAndWrite(w)
🚧 Under Construction 🚧 TODO: Move into new package UTL_CGI
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